OR I G I N A L A R T I C L E Hurricane-induced changes in mayfly assemblage structure, production and emergence in a tropical island stream Cambios inducidos por los huracanes en la estructura, producción, y emergencia del ensamblaje de Ephemeroptera de una quebrada de isla tropical Alonso Ramírez1 | Ana M. Meza-Salazar1 | Jesús E. Gómez2,3 | Pablo E. Gutiérrez-Fonseca4 | José Sánchez-Ruiz5† 1Department of Applied Ecology, North Carolina State University, Raleigh, North Carolina, USA 2Department of Environmental Sciences, University of Puerto Rico–Río Piedras, San Juan, Puerto Rico 3Department of Biological Sciences, Florida International University, Miami, Florida, USA 4Rubenstein School of Environment and Natural Resources, University of Vermont, Burlington, Vermont, USA 5Department of Ecology, Montana State University, Bozeman, Montana, USA Correspondence Alonso Ramírez, Department of Applied Ecology, North Carolina State University, 100 Eugene Brooks Avenue, Raleigh, NC 27695-7617, USA. Email: alonso.ramirez@ncsu.edu Funding information National Science Foundation, Grant/Award Number: DEB-1831952 Associate Editor: Marija Ivkovi�c Abstract 1. Hurricanes are major disturbances with important consequences to stream ecosys- tems as they create major floods and remove riparian vegetation. Understanding their impacts is a priority, as hurricane intensity is expected to increase due to global climate change. 2. Mayfly assemblages in streams fill a diversity of ecological roles and functions. They are important consumers of algae by scraping benthic biofilms and detritivores associated with fine particles and leaf litter. Other taxa are filterers and even preda- tors. Mayflies are also important prey items in aquatic and terrestrial food webs. 3. Here, we assessed the effects of two consecutive hurricanes that impacted Puerto Rico in 2017 to understand how hurricane-induced changes in the environment alter mayfly composition, secondary production and emergence. 4. The study was conducted in the Luquillo Experimental Forest, Puerto Rico. Mayflies were sampled as nymphs and emerging adults for 6 months before and 17 months after hurricanes Irma and María hit the island in September 2017. Leaf litter inputs, canopy cover and chlorophyll a concentrations were monitored along with mayflies. † Deceased. Received: 16 June 2023 Accepted: 9 October 2024 DOI: 10.1111/een.13394 This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made. © 2024 The Author(s). Ecological Entomology published by John Wiley & Sons Ltd on behalf of Royal Entomological Society. Ecological Entomology. 2025;50:201–213. wileyonlinelibrary.com/journal/een 201 https://orcid.org/0000-0001-9985-5719 https://orcid.org/0000-0003-1331-5952 https://orcid.org/0009-0007-9276-8971 https://orcid.org/0000-0003-0777-8889 https://orcid.org/0000-0003-4383-8017 mailto:alonso.ramirez@ncsu.edu http://creativecommons.org/licenses/by-nc-nd/4.0/ http://wileyonlinelibrary.com/journal/een http://crossmark.crossref.org/dialog/?doi=10.1111%2Feen.13394&domain=pdf&date_stamp=2024-10-24 5. Mayfly assemblages were dominated by two genera of Leptophlebiidae before the hurricane, Neohagenulus (two species: N. julio Traver, 1938, N. luteolus Traver, 1938) and Borinquena (one species: B. carmencita Traver, 1938). Both genera decreased in density after the hurricanes and were replaced with the Baetidae Cloeodes macu- lipes Traver, 1938 as the dominant taxon. This pattern was observed in both nymph and emerging adult densities. 6. The secondary production of Leptophlebiidae species was highest before hurricane disturbance, with the Baetidae C. maculipes showing the opposite pattern. Neoha- genulus had an annual production of 445 mg m�2 year�1, C. maculipes of 153 mg m�2 year�1 and B. carmencita of 68 mg m�2 year�1. 7. Overall, the mayfly assemblages in our studied stream are vulnerable to hurricane disturbances. Expected increases in hurricane impacts might result in assemblage shifts that could change assemblage composition and alter energy flows within the ecosystem. K E YWORD S assemblage composition, Ephemeroptera, hurricane disturbance, secondary production, tropical streams INTRODUCTION Hurricanes are major climatic events that have devastating and long- lasting effects on natural ecosystems, altering community structure and food webs (Patrick et al., 2022). Heavy precipitation during a storm creates major floods in streams that, through flood disturbance, lead to displacement and increased mortality of aquatic organisms (Resh et al., 1988). Hurricane floods modify stream habitat availability by altering channel geomorphology, exporting large amounts of organic matter and creating debris dams (Wohl et al., 2019). Although flood disturbance has large negative impacts on aquatic populations (Resh et al., 1988), many species are resistant or resilient to them. For example, freshwater decapods in Puerto Rico were not severely affected by hurricane floods (Covich et al., 2006) and aquatic insects with short life cycles are expected to recover quickly from flood dis- turbances (Lytle, 2002). A lasting disturbance associated with hurricanes is the damage they inflict on riparian vegetation. Hurricane winds remove leaves and small branches, defoliating riparian vegetation and creating a single large pulse of detritus (Walker et al., 1991). Most of that material is either exported downstream or temporarily trapped in debris dams (Wohl et al., 2019). Defoliation increases the amount of solar radiation reaching the stream (Fernández & Fetcher, 1991). Thus, small headwa- ter streams that are often detritus-based ecosystems switch to alga- based ecosystems for several years after hurricane disturbance (Gutiérrez-Fonseca et al., 2024), as riparian vegetation recovery can take up to 6 years (Zimmerman et al., 2021). This change in basal resources might change aquatic insect assemblage composition, favour- ing herbivores over detritivores as observed in response to watershed deforestation (Benstead & Pringle, 2004). However, there is still a lack of information on how aquatic insect assemblages respond to hurricane defoliation of riparian forests (Strickland et al., 2024). Understanding hurricane impacts on ecosystems is critical, given climate change projections. Major hurricanes impact terrestrial eco- systems annually, with some geographic locations experiencing more storms than others. However, climate change models predict increases in storm intensity, and major hurricanes are expected to become more frequent (Knutson et al., 2020; Walsh et al., 2016). His- torically, major hurricane impacts on Caribbean islands are relatively infrequent. Puerto Rico, for example, was expected to experience them with a recurrence interval of 50–60 years up to the 1990s (Scatena & Larsen, 1991). This frequency has increased over the past decades. The last four major hurricanes affecting Puerto Rico were Hugo in 1989, Georges in 1998 and, more recently, Irma and María in 2017, four major hurricane impacts in only 28 years. Mayflies (Ephemeroptera) are a dominant group of aquatic insects that play multiple roles in stream ecosystems, mostly as primary con- sumers (Domínguez et al., 2006). Most species of mayflies have nymphs that can be considered scrapers/grazers, which feed on algae over hard surfaces in the stream bottom, or collector gatherers, which consume fine particles by collecting them from the bottom (Ramírez & Gutiérrez-Fonseca, 2014). In Puerto Rico, where this study took place, mayflies form part of both feeding groups (Gutiérrez-Fonseca et al., 2013). Mayfly adults are short-lived, reproducing and dying soon after emerging from the aquatic environment. Even so, they are an important energy source for both aquatic and terrestrial food webs (Rosas et al., 2020). For example, riparian consumers (e.g. spiders and lizards) are well adapted to catching and consuming emerging may- flies, thus linking aquatic and terrestrial ecosystems (Kelly et al., 2015). Therefore, mayflies represent an ideal group for studying the effects of hurricane disturbance on stream ecosystems, specifi- cally their effects on habitats and the availability of food resources, as their assemblages are composed of species that rely on detritus and others that consume algae. 202 RAMÍREZ ET AL. 13652311, 2025, 1, D ow nloaded from https://resjournals.onlinelibrary.w iley.com /doi/10.1111/een.13394 by M ontana State U niversity L ibrary, W iley O nline L ibrary on [27/01/2025]. See the T erm s and C onditions (https://onlinelibrary.w iley.com /term s-and-conditions) on W iley O nline L ibrary for rules of use; O A articles are governed by the applicable C reative C om m ons L icense Here, we assessed how hurricane impacts change environmental conditions in tropical streams and how those changes alter mayfly assemblages in a headwater stream in Puerto Rico. Our objectives were to (1) describe the effect of hurricane disturbance on mayfly assem- blages, secondary production and emergence; (2) determine potential environmental drivers behind changes in mayfly assemblages; and (3) assess the relation between assemblages and time since hurricane impact using available data. We predict that changes in mayfly assem- blages would be associated with hurricane defoliation of riparian for- ests, increases in solar radiation and algal biomass. As the studied rainforest stream floods frequently in response to heavy rains, we did not expect major changes associated with hurricane floods. MATERIALS AND METHODS Study site Our study stream, Quebrada Prieta, is in the Luquillo Experimental Forest (LEF) in north-eastern Puerto Rico (18�190 N, 65�450 W; Figure 1). The LEF is an aseasonal forest where heavy precipitation might occur at any point during the year (Gutiérrez-Fonseca et al., 2020). The mean annual precipitation (1975–2016) is 3676 mm at 350 m above sea level, ranging from 1405 mm year�1 in 1994 to 5567 mm year�1 in 2010 (Gutiérrez-Fonseca et al., 2020). The diurnal and mean annual air temperatures above the canopy are 21–25�C (McDowell et al., 2012). Quebrada Prieta is a second-order stream within the Espíritu Santo watershed. Prieta has a steep channel composed of a series of pools separated by drops or steps and a few small riffles. The domi- nant substrates are boulders and large cobbles with gravel, sand and silt deposited in pools. We selected pools as our focal study habitat along two tributaries of Prieta (i.e. arms A and B) draining primary for- ests (�400 m asl). Riparian vegetation is dominated by tabonuco trees (Dacryodes excelsa Vahl, Burseraceae) and sierra palms (Prestoea acu- minata (Willd.), Arecaceae). Aquatic insect assemblages are dominated by the orders Ephemeroptera, Odonata, Trichoptera, Lepidoptera, Coleoptera and Diptera (Gutiérrez-Fonseca et al., 2020; Ramírez & Hernández-Cruz, 2004). Eight species of decapods occur in our study stream, but two omnivorous ones are dominant in density and bio- mass: Atya lanipes Holthuis, 1963 (Atyidae) and Xiphocaris elongata Guérin-Méneville, 1855 (Xiphocarididae; Cross et al., 2008). The green stream goby, Sicydium spp. (Gobiidae; there are several pos- sible species), is the only fish taxon present in Prieta. A previous study in Quebrada Prieta by Pescador et al. (1993) reported mayfly assemblages composed of three genera and at least F I GU R E 1 Quebrada Prieta, arms A and B, located in the Luquillo Experimental Forest (LEF) in Puerto Rico, was affected by hurricanes Irma and María in September 2017. The path of María is shown with numbers indicating hurricane intensity in the Saffir–Simpson scale. Photos contrast the stream before and after the hurricane. Photos by P. E. Gutiérrez-Fonseca. HURRICANE-INDUCED CHANGES IN MAYFLY ASSEMBLAGES 203 13652311, 2025, 1, D ow nloaded from https://resjournals.onlinelibrary.w iley.com /doi/10.1111/een.13394 by M ontana State U niversity L ibrary, W iley O nline L ibrary on [27/01/2025]. See the T erm s and C onditions (https://onlinelibrary.w iley.com /term s-and-conditions) on W iley O nline L ibrary for rules of use; O A articles are governed by the applicable C reative C om m ons L icense four species. Leptophlebiidae had two species of Neohagenulus, Neo- hagenulus julio Traver, 1938 and Neohagenulus luteolus Traver, 1938, and one species of Borinquena, Borinquena carmencita Traver, 1938. In Baetidae, only the genus Cloeodes was found, represented by only one species, Cloeodes maculipes Traver, 1938. Hurricane history at the LEF Major hurricanes deposit large amounts of precipitation over short periods, creating floods and pulses of sediment and particles. How- ever, the headwater streams in the LEF, like our study stream, have small watersheds and are naturally flashy. Thus, hurricane-size floods are common disturbances. In contrast, the impact of hurricane winds creates new environmental conditions in and around streams by removing the forest canopy (Leitold et al., 2022). Canopy defoliation creates a major pulse of debris (Liu et al., 2018), which have short- term impacts, as streams process or export that material within a few months (Covich et al., 1991). This initial pulse of leaf litter is followed by a post-hurricane period with minimal litter inputs that can last sev- eral years (Zimmerman et al., 2021). A more open canopy increases the amount of solar radiation reaching the stream. Stream channels that are normally heavily shaded (up to 95% canopy cover) become sunny, and their water temperature increases. In past decades, the LEF has experienced four major hurricane impacts. Hurricane Hugo impacted the LEF in 1989 after a long period without major storm disturbances (Scatena & Larsen, 1991). Hugo reduced the canopy cover significantly, depositing major amounts of debris on the forest floor. Hurricane Georges impacted the LEF 9 years after Hugo, in 1998. Similarly, Georges reopened the canopy cover over streams. In September 2017, the LEF was struck by two major hurricanes in close succession. Hurricane Irma had minor impacts on the forest as it passed north of Puerto Rico. Hurricane María had a path closer to the LEF with major impacts on the forest and streams (Figure 1). Here, we mainly refer to María, but impacts are the combined effects of both Irma and María. Environmental variables Stream discharge is automatically monitored at various locations in Prieta; we are presenting data for the monitoring station located downstream from the confluence of arms A and B, as it represents the main stem of Prieta. Discharge is obtained by measuring the water level with a pressure transducer (Onset Computers, U20L-01) every 15 min and applying a gauge-discharge equation developed for the monitoring location. Canopy cover is measured with a spherical densi- ometer at 12 points over the 100-m reach of arms A and B. Measures were taken bimonthly before the 2017 hurricanes and monthly after the hurricanes. We are presenting canopy cover as monthly averages for both arms. Algal chlorophyll a was measured by collecting monthly samples in six pools in each arm of Prieta by collecting six subsamples per pool using a modified Loeb sampler (Loeb, 1981). Subsamples were mixed, and chlorophyll was analysed using a fluorometer following extraction with ethanol, according to standard methods (APHA, 2005). Ten leaf litter baskets hanging over the channel in each of arms A and B (20 baskets total) were used to monitor the vertical inputs of leaf lit- ter. Baskets were emptied every 2 weeks and were oven-dried at 70�C for 48 h; data are presented as grams per square metre per day. Benthic organic matter (BOM) was measured from mayfly nymph samples (see details below). BOM was dried at 70�C for 48 h and ashed at 500�C to present data as grams of ash-free dry mass (AFDM) per square metre. Mayfly assemblages Mayfly nymphs were sampled monthly from January 2017 to December 2018. Samples were collected in six pools along a 100-m reach in arms A and B using a corer sampler (0.0314 m2). The corer was pushed into the substrate to a depth of 10 cm or until reaching bedrock. The benthic substrate was placed into a bucket and stirred before pouring it through a 250-μm sieve. The material retained in the sieve was placed in bags and preserved with formaldehyde (�5% solution after diluting with stream water) and later transferred to eth- anol (80%). Mayflies were separated from debris and identified using keys in Peters (1971) and Salles et al. (2018). Nymphs of the two species of Neohagenulus are difficult to separate and are reported at the genus level. The individual length was measured to the nearest 0.5 mm, and biomass was obtained by applying the length–mass regressions from Benke et al. (1999). Although regressions in Benke et al. (1999) are biased towards organisms from temperate regions, we currently lack these relations for most tropical taxa. Mayfly density and biomass were expressed as number of individuals per square metre and milli- grams of AFDM per square metre, respectively. Secondary production was estimated by applying the instantaneous growth method (Benke & Huryn, 2017) using growth rates from Rosas et al. (2020). Mayfly production was expressed as milligrams of AFDM per square metre per month. Adult emergence was sampled monthly from February 2017 to December 2018 using emergence traps placed over pools. Traps are pyramid-shaped with a sampling area of 0.50 m2 and were deployed monthly for four consecutive days, allowing for the collection of subi- magos and imagos. After that period, specimens remaining in the net were removed using an aspirator and added to the sample container. Samples were preserved in 80% ethanol, and specimens were identi- fied to the species level using Traver (1938) and Peters (1971). Indi- vidual length was measured to the nearest 0.5 mm, and biomass was obtained by applying the length–mass regressions from Sabo et al. (2002). The density of emerging adults was expressed as individuals per square metre per day. Comparisons with previous hurricane impacts were possible using mayfly emergence data from previous studies. Data for post-hurricane Hugo were available from Pescador et al. (1993). They collected 204 RAMÍREZ ET AL. 13652311, 2025, 1, D ow nloaded from https://resjournals.onlinelibrary.w iley.com /doi/10.1111/een.13394 by M ontana State U niversity L ibrary, W iley O nline L ibrary on [27/01/2025]. See the T erm s and C onditions (https://onlinelibrary.w iley.com /term s-and-conditions) on W iley O nline L ibrary for rules of use; O A articles are governed by the applicable C reative C om m ons L icense mayfly emergence during 1990, starting 6 months after Hurricane Hugo hit Puerto Rico in 1989. In a second study, the lead author col- lected data for post-hurricane Georges in 2003, 5 years after Georges hit Puerto Rico in 1998 (Ramírez, unpublished data). Mayflies were collected in arm B monthly for 1 year. Traps were sampled continu- ously, and sampling containers were cleaned once a month. Consider- ing that different data sets used different sampling efforts, we compared only the per cent contribution of each mayfly species to the total assemblage. Statistical analysis Pre- versus post-hurricane comparisons of nymph and adult densities and biomass were assessed using a t-test or Wilcoxon signed-rank test depending on whether the data were normally distributed or not using the Shapiro–Wilk test. We used regression analysis to relate changes in environmental variables (i.e. canopy, leaf litter inputs) with mayfly density and biomass. Analyses were run in R version 4.1.3 (R Core Team, 2022). RESULTS Hurricane impacts Quebrada Prieta has a flashy hydrograph that reflects its aseasonal environment (Figure 2a,b). Stream hydrographs suggest that floods produced by heavy precipitation during Hurricane Irma were within the range of those observed during other times of the year, as either average daily discharge (Figure 2a) or maximum daily discharge (Figure 2b). During Hurricane María, our gauge was briefly damaged by debris falling from riparian trees, and our measure of peak dis- charge may be an underestimation. Hurricane winds defoliated most F I GU R E 2 Daily average (a) and maximum (b) stream discharges and canopy cover (c) over Quebrada Prieta for the duration of the study, from January 2017 to December 2018. Points in panel (c) are monthly averages and standard error. The vertical yellow line indicates the impact of Hurricane María. HURRICANE-INDUCED CHANGES IN MAYFLY ASSEMBLAGES 205 13652311, 2025, 1, D ow nloaded from https://resjournals.onlinelibrary.w iley.com /doi/10.1111/een.13394 by M ontana State U niversity L ibrary, W iley O nline L ibrary on [27/01/2025]. See the T erm s and C onditions (https://onlinelibrary.w iley.com /term s-and-conditions) on W iley O nline L ibrary for rules of use; O A articles are governed by the applicable C reative C om m ons L icense of the riparian forest, and canopy cover went from �85% before the hurricanes to about 20% after the hurricanes (Figure 2c). Recovery was evident, and canopy cover reached �60% by the end of our study (Figure 2c). Assemblages and temporal trends We found two families and four species of mayflies in Quebrada Prieta (Figure 3). In the family Leptophlebiidae, N. julio was the most frequently found species, with a few individuals of N. luteolus present. Separating small individuals of these two taxa as nymphs is difficult, we refer to the group as Neohagenulus, and it was the most abundant taxon (monthly nymph density ranged from 18 to 443 ind m�2), followed by B. carmencita (nymph density: 0–437 ind m�2). In Baeti- dae, the only species present was C. maculipes with nymph densities ranging from 0 to 510 ind m�2 (Table 1). Leptophlebiidae were abundant before the hurricane and decreased considerably after (Table 2). Nymphs of B. carmencita had a peak in den- sity and biomass during July 2017 and then remained at low values for the remainder of the study period (Figure 3a,d). Neohagenulus density and biomass fluctuated before the hurricane and presented a peak right after the hurricane (October 2017), and then values remained low for the entire post-hurricane study period (Figure 3b,e). The Baetidae C. maculipes had the opposite pattern. Density and biomass were low before the hurricane and peaked a few months after, returning to low values in the last 3 months of our study period (Figure 3c,f). Means and ranges for density and biomass are presented in Table 1. F I GU R E 3 Mayfly nymph density and biomass at Quebrada Prieta for Borinquena carmencita (a, d), Neohagenulus spp. (b, e) and Cloeodes maculipes (c, f). The vertical yellow line indicates the impact of Hurricane María. Points are monthly averages and standard errors. 206 RAMÍREZ ET AL. 13652311, 2025, 1, D ow nloaded from https://resjournals.onlinelibrary.w iley.com /doi/10.1111/een.13394 by M ontana State U niversity L ibrary, W iley O nline L ibrary on [27/01/2025]. See the T erm s and C onditions (https://onlinelibrary.w iley.com /term s-and-conditions) on W iley O nline L ibrary for rules of use; O A articles are governed by the applicable C reative C om m ons L icense T AB L E 1 Density, biomass, secondary production and biomass turnover (production/biomass [P/B]) for each major taxon in Quebrada Prieta. Nymphs Density (individuals m�2) Biomass (mg m�2) Production P/BMean Range Mean Range (mg m�2 time�1)a Borinquena Pre 101.15 21.23–437.93 3.78 0.40–11.10 11.19 Post 40.69 0.00–111.47 1.02 0.00–3.69 3.37 Annual 63.37 2.05 68.50 33.30 Neohagenulus Pre 164.55 29.19–339.73 22.72 5.31–52.15 48.71 Post 87.23 18.58–443.25 18.31 3.07–132.53 33.33 Annual 116.23 19.96 444.82 22.28 Cloeodes Pre 29.20 0.00–90.24 1.17 0.00–3.74 2.97 Post 150.40 13.27–509.60 9.20 1.82–29.40 18.83 Annual 104.95 6.19 153.16 24.74 Emergence Density (ind m�2 day�1) Biomass (mg m�2 day�1) Mean Range Mean Range Borinquena Pre 0.53 0.00–1.63 0.35 0.00–0.79 Post 0.50 0.00–1.98 0.29 0.00–1.16 Annual 0.51 0.31 Neohagenulus Pre 2.93 0.61–6.78 2.41 0.45–5.39 Post 1.51 0.51–6.29 1.09 0.27–4.40 Annual 2.02 1.58 Cloeodes Pre 0.52 0.00–1.14 0.25 0.00–0.55 Post 2.25 0.64–5.19 1.13 0.37–2.69 Annual 1.62 0.81 Note: Values for pre- and post-hurricane are monthly means; annual values are per year. aPre- and post-hurricane production is presented as monthly (mg m�2 month�1); annual production is presented as per year (mg m�2 year�1). T AB L E 2 Before–after hurricane effects on mayfly nymphs and adults in Quebrada Prieta. Density Biomass Production W p-Value W p-Value W p-Value Nymphs Borinquena 41.50 ns 24.00 0.01 15.00 0.01 Neohagenulus 30.50 0.03 31.00 0.03 24.00 0.03 Cloeodes 113.00 0.01 124.00 <0.01 105.00 <0.01 Emergence Borinquena 46.00 ns 47.00 ns Neohagenulus* 26.00 0.05 25.00 0.04 Cloeodes 109.00 <0.01 108.00 <0.01 Note: See Figure 5 for direction of changes. All effects were evaluated with Wilcoxon tests (W), except for Neohagenulus, which was evaluated with t-tests (indicated by *). ns = not significant. HURRICANE-INDUCED CHANGES IN MAYFLY ASSEMBLAGES 207 13652311, 2025, 1, D ow nloaded from https://resjournals.onlinelibrary.w iley.com /doi/10.1111/een.13394 by M ontana State U niversity L ibrary, W iley O nline L ibrary on [27/01/2025]. See the T erm s and C onditions (https://onlinelibrary.w iley.com /term s-and-conditions) on W iley O nline L ibrary for rules of use; O A articles are governed by the applicable C reative C om m ons L icense Adult emergence followed the same general temporal patterns described for nymphs, except that B. carmencita was always present at low densities and biomass (Figure 4a,d). Neohagenulus had a peak in emergence during May and June and then in December 2017 (Figure 4b,e). Cloeodes maculipes emergence followed a pattern similar to that of the nymphs, with low values during pre-hurricane months and then increasing during post-hurricane, with a return to low values during the last months of our sampling period (Figure 4c,f). Means and ranges for density and biomass are presented in Table 1. Comparing pre- and post-hurricane periods, we found the same patterns described for monthly samples (Figure 5, Table 2). Neohagen- ulus had significantly higher density, biomass, production and emer- gence before the hurricane. In contrast, B. carmencita showed higher variability and only differences in biomass and production were signif- icantly higher during the pre-hurricane period (Table 2). Cloeodes maculipes followed the opposite pattern. It was significantly more abundant after the hurricane (Figure 5; Table 2). In the case of C. maculipes, pre versus post differences were large, with values after the storm up to two to three times higher than pre-hurricane (Figure 5). Neohagenulus was the most productive taxon during all periods, and the highest production was during the pre-hurricane period (aver- age monthly production: 48.71 mg m�2 month�1; Table 1). The lowest monthly production was for C. maculipes during the pre-hurricane period (average monthly production: 2.97 mg m�2 month�1; Table 1). Calculating production based on the calendar year resulted in annual production values that ranged from 444.82 mg m�2 year�1 for Neoha- genulus and 68.50 mg m�2 year�1 for B. carmencita, with C. maculipes falling in the middle with 153.16 mg m�2 year�1 (Table 1). Corre- sponding production/biomass (P/B) ratios based on annual production ranged from 22.28 (Neohagenulus) to 33.30 (B. carmencita) and 24.74 for C. maculipes (Table 1). F I GU R E 4 Mayfly adult emergence density and biomass at Quebrada Prieta for Borinquena carmencita (a, d), Neohagenulus spp. (b, e) and Cloeodes maculipes (c, f). The vertical yellow line indicates the impact of Hurricane María. Points are monthly averages and standard errors. 208 RAMÍREZ ET AL. 13652311, 2025, 1, D ow nloaded from https://resjournals.onlinelibrary.w iley.com /doi/10.1111/een.13394 by M ontana State U niversity L ibrary, W iley O nline L ibrary on [27/01/2025]. See the T erm s and C onditions (https://onlinelibrary.w iley.com /term s-and-conditions) on W iley O nline L ibrary for rules of use; O A articles are governed by the applicable C reative C om m ons L icense Only two environmental variables were significantly related to nymph or adult density or biomass. Leaf litter inputs were positively related to Neohagenulus and B. carmencita nymph density and biomass (Table 3). Leaf litter was negatively related to C. maculipes adult emergence (Table 3). Similarly, the ratio between chlorophyll a concentration and leaf litter inputs was F I GU R E 5 Hurricane impacts on mayfly assemblages in Quebrada Prieta. (a) Nymph density, (b) nymph biomass, (c) adult emergence density, (d) adult emergence biomass and (e) secondary production. PostH, post-hurricane; PreH, pre-hurricane. Points indicate outliers. HURRICANE-INDUCED CHANGES IN MAYFLY ASSEMBLAGES 209 13652311, 2025, 1, D ow nloaded from https://resjournals.onlinelibrary.w iley.com /doi/10.1111/een.13394 by M ontana State U niversity L ibrary, W iley O nline L ibrary on [27/01/2025]. See the T erm s and C onditions (https://onlinelibrary.w iley.com /term s-and-conditions) on W iley O nline L ibrary for rules of use; O A articles are governed by the applicable C reative C om m ons L icense significantly related to Neohagenulus and B. carmencita nymph den- sity and biomass, but not to their adults or nymphs and adults of C. maculipes (Table 3). Cloeodes maculipes nymph biomass and adult density and biomass were all negatively related to canopy cover (Table 3). Past hurricanes and emergence Our samples from pre-hurricane María represent stream conditions from a period of �20 years without a major hurricane impacting Puerto Rico. Samples collected post-Hugo and those from post-María represent periods immediately after a major hurricane impact. Our 5-year post-Georges data are representative of post-recovery of hur- ricane disturbance (Figure 6). Leptophlebiidae dominated mayfly assemblages during periods without hurricane disturbance (i.e. pre-María and the 5-year post- Georges), with a larger number of B. carmencita in the recovery period post-Georges (Figure 6). In contrast, both post-hurricane periods (i.e. post-María and post-Hugo) have dominance by C. maculipes and reduced proportions of Neohagenulus, with B. carmencita contributing a small fraction (Figure 6). DISCUSSION Our study found low mayfly taxon richness in the studied stream simi- lar to that previously reported for our area (Pescador et al., 1993). Puerto Rico is an oceanic island with low species richness relative to that of continental areas, including few aquatic insect taxa (Gutiérrez- Fonseca et al., 2013). The families recorded, Leptophlebiidae and T AB L E 3 Regression analysis between Ephemeroptera taxa and environmental variables. Leaf litter Chlorophyll/leaf litter Canopy cover Borinquena Nymph density 0.61 0.59 ns Nymph biomass 0.69 0.71 ns Adult density ns ns ns Adult biomass ns ns ns Secondary production 0.21 0.17 ns Neohagenulus Nymph density 0.61 0.59 ns Nymph biomass 0.69 0.71 ns Adult density ns ns ns Adult biomass ns ns ns Secondary production 0.37 0.43 ns Cloeodes Nymph density ns ns ns Nymph biomass ns ns �0.30 Adult density �0.17 ns �0.46 Adult biomass ns ns �0.46 Secondary production �0.21 �0.15 �0.33 Note: Only significant relations at p < 0.05 are presented; values are regression coefficients. ns = not significant. F I GU R E 6 Mayfly adult emergence composition in Quebrada Prieta in relation to recent hurricane disturbances: Hugo in 1989, Georges in 1998 and María in 2017. The vertical axis shows the proportion of individuals per genus during each period. 210 RAMÍREZ ET AL. 13652311, 2025, 1, D ow nloaded from https://resjournals.onlinelibrary.w iley.com /doi/10.1111/een.13394 by M ontana State U niversity L ibrary, W iley O nline L ibrary on [27/01/2025]. See the T erm s and C onditions (https://onlinelibrary.w iley.com /term s-and-conditions) on W iley O nline L ibrary for rules of use; O A articles are governed by the applicable C reative C om m ons L icense Baetidae, are species-rich and abundant in streams globally (Barber- James et al., 2007). We expected these two families to display similar responses to hurricane disturbance. Our findings support the expected change in assemblage abundance, biomass and secondary production following the hurricane, but the contrasting responses by different taxa were unexpected. The most significant changes in mayfly assemblages are likely associated with shifts in habitat and energy resources. Leptophlebii- dae were predominantly found in microhabitats with leaf litter and at the underside of rocks, whereas Baetidae were common on hard sub- strates lacking detritus (AR’s and JEG’s personal observations). Hurri- canes significantly reduce leaf litter inputs after an initial pulse during the storm and increase solar radiation, increasing algal productivity (Wohl et al., 2019). This pulse of leaf litter is short-lived, as most are quickly exported downstream during floods, with the remaining por- tion rapidly consumed or decomposed. Leptophlebiidae appears to respond to leaf litter availability, as they had a short-lived peak in den- sity, biomass and emergence in the months following the hurricane and then decreased to low values (e.g. Figure 2). In contrast, Baetidae responses were more closely associated with the increase in solar radiation, with nymphs peaking 6 months after the hurricane, but adult emergence began even early. Changes in energy resources fur- ther explain differences in the response of these mayflies to hurricane disturbance. Stable isotope analysis indicates that both mayfly families continued relying on allochthonous carbon as their primary energy source after the hurricane (Gutiérrez-Fonseca et al., 2024). Mean- while, freshwater shrimps, the dominant consumer in the studied stream, shifted their diets towards algae (Gutiérrez-Fonseca et al., 2024), potentially intensifying competition and predation pressure on mayflies. The impact of hurricanes Irma and María profoundly changed terrestrial and aquatic ecosystems in our study area. The change in resource availability that we observed (leaf litter vs. epilithic algae) and changed mayfly assemblages are similar to findings reported for terrestrial insect assemblages. In seasonal tropical dry forests, changes in the relative abundance of different groups of consumers occurred after hurricane defoliation of forest canopy. Several taxa of herbivo- rous insects and one of predatory beetles increased in density after hurricane disturbance in Mexico (Novais et al., 2018). Canopy insects in Puerto Rico have complex responses to hurricane disturbance that result from the interaction between the plant host and the environ- mental conditions (Schowalter & Ganio, 1999). In our study, effects were indirect, via changes in leaf litter availability and solar radiation over the stream channel. Hurricanes impact stream ecosystems also via heavy precipitation and flooding. In montane areas, like our study region, hurricane pre- cipitation is often intense and results in major floods. However, our stream discharge monitoring highlights that major floods occur fre- quently in these headwater streams and are not exclusively associated with hurricanes (see Figure 2a). North-eastern Puerto Rico is the wet- test part of the island, with trade winds carrying moisture from the Atlantic Ocean and tropical storms affecting the island during the hur- ricane season. Mayflies in Prieta appear well adapted to flooding, and although the hurricane flood potentially impacted them, those impacts were not evident during our study. Although our monthly sampling might have missed some peaks in nymph density or adult emergence, the overall pattern was clear. Secondary production of both families was within or above the range reported by previous studies in Luquillo for streams under closed canopy. For instance, the annual production of N. julio ranged from 425 to 556 mg m�2 year�1 (Rosas et al., 2020). In contrast, the same authors recorded lower production of C. maculipes (41–58 mg m�2 year�1) compared with our results, which are most likely a result of hurricane effects. This is the first time that secondary production of B. carmencita was measured (68 mg m�2 year�1). Sec- ondary production of tropical aquatic insects tends to be lower than reports from temperate streams. One exception is Leptophlebiidae mayflies that have similar production in both regions (Rosas et al., 2020). Turnover ratios (P/B) are good indicators of biomass turnover over a time period (Benke, 1984). In our study area, both Neohagenulus and Cloeodes can be expected to have ratios around 20, indicating that populations replace their biomass 20 times per year (Rosas et al., 2020). We measured similar ratios in our annual esti- mates, ranging between 22 for Neohagenulus and 25 for Cloeodes, respectively, and even higher for Borinquena (P/B = 33). The responses to hurricane disturbance were similar in terms of produc- tion and densities. Both Leptophlebiidae genera decreased their pro- ductivity, whereas that of Cloeodes increased. The higher variability observed in the response of Neohagenulus could be associated with the short-lived pulse of leaf litter following the hurricane. Disturbances that remove riparian vegetation and increase solar radiation over streams, like hurricanes, often increase the productivity of grazers to the detriment of detritivorous macroinvertebrates. For example, selective logging that removed tree cover in the margins of an Appalachian stream increased Baetidae secondary production by up to 17 times that of a reference forest stream (Wallace & Gurtz, 1986). Through gut content analysis, the same study found the increase in productivity to be associated with higher diatom availabil- ity. Similarly, in tropical streams in Madagascar, deforestation enhances the biomass of a few collector-gatherer taxa that can take advantage of enhanced algal resources, whereas most forest- associated taxa are absent from streams that lack leaf litter resources (Benstead & Pringle, 2004). Those findings agree with ours, indicating that changes in riparian vegetation are important drivers of assem- blage composition and productivity. Long-term hurricane impacts The mayfly assemblages in our study stream were shown to be vul- nerable to hurricane disturbances, via their effects on riparian forests. The observed changes in mayfly assemblages were significant and lasted for over a year following the hurricane. Species in our study stream are multivoltine and have relatively short life cycles (Rosas et al., 2020); thus, hurricane disturbance impacted several generations. It can be expected that populations will return to pre- HURRICANE-INDUCED CHANGES IN MAYFLY ASSEMBLAGES 211 13652311, 2025, 1, D ow nloaded from https://resjournals.onlinelibrary.w iley.com /doi/10.1111/een.13394 by M ontana State U niversity L ibrary, W iley O nline L ibrary on [27/01/2025]. See the T erm s and C onditions (https://onlinelibrary.w iley.com /term s-and-conditions) on W iley O nline L ibrary for rules of use; O A articles are governed by the applicable C reative C om m ons L icense disturbance conditions once riparian vegetation recovers from defolia- tion and re-establish leaf litter inputs into the stream. However, forest recovery is slow and takes more than 5 years (Brokaw et al., 2012; Zimmerman et al., 2021). As mayflies are among the most abundant aquatic insects in the LEF (Ramírez & Hernández-Cruz, 2004) and in streams in general (Domínguez et al., 2006), we suggest that changes in their abundance could cascade into other compartments of the eco- system, including aquatic (e.g. dragonflies and shrimps) and terrestrial predators (e.g. spiders and anoles lizards). Projections of an increase in hurricane frequency and intensity, with more intense storms affecting the Caribbean islands and coastal regions of North America expected in the coming years (Knutson et al., 2020; Walsh et al., 2016), may result in long-term changes in insect assemblages. An increase in hurricane disturbance could delay riparian recovery and extend the duration of hurricane impacts on aquatic populations. Based on mayfly responses, increases in hurricane disturbance frequency could result in a shift in community composition and a potentially change in the energy flow. Similar changes in insect assemblages have been reported for other hurricane impacted aquatic (Strickland et al., 2024) and terrestrial ecosystems (Novais et al., 2018), highlighting the importance of understanding how recurrent disturbances might result in new ecosystem dynamics. AUTHOR CONTRIBUTIONS Alonso Ramírez: Conceptualization; investigation; funding acquisition; writing – original draft; methodology; writing – review and editing; formal analysis; project administration; data curation; supervision; visualization. Ana M. Meza-Salazar: Investigation; writing – review and editing; writing – original draft; formal analysis. Jesús E. Gómez: Writing – original draft; investigation; methodology; writing – review and editing; data curation. Pablo E. Gutiérrez-Fonseca: Conceptuali- zation; writing – original draft; methodology; writing – review and editing; formal analysis; investigation; data curation. José Sánchez- Ruiz: Writing – original draft; writing – review and editing; formal analysis; investigation. ACKNOWLEDGEMENTS This manuscript is dedicated to the memory of our friend and col- league José ‘Tosti’ Sánchez-Ruiz, who passed away in September 2023. This study is part of the Luquillo LTER program (National Sci- ence Foundation, DEB-1831952). Data collection was possible thanks to the participation of our StreamFRE team, including technicians, vol- unteers and students. CONFLICT OF INTEREST STATEMENT The authors declare no conflicts of interest. DATA AVAILABILITY STATEMENT The data that support the findings of this study are openly available in the EDI Data Portal at https://portal.edirepository.org/nis/ mapbrowse?packageid=knb-lter-luq.227.2. ORCID Alonso Ramírez https://orcid.org/0000-0001-9985-5719 Ana M. Meza-Salazar https://orcid.org/0000-0003-1331-5952 Jesús E. Gómez https://orcid.org/0009-0007-9276-8971 Pablo E. Gutiérrez-Fonseca https://orcid.org/0000-0003-0777- 8889 José Sánchez-Ruiz https://orcid.org/0000-0003-4383-8017 REFERENCES APHA. (2005) Standard methods for the examination of water and wastewa- ters. Washington, DC: American Public Health Association, p. 1368. Barber-James, H.M., Gattolliat, J.L., Sartori, M. & Hubbard, M.D. (2007) Global diversity of mayflies (Ephemeroptera, Insecta) in freshwater. 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How to cite this article: Ramírez, A., Meza-Salazar, A.M., Gómez, J.E., Gutiérrez-Fonseca, P.E. & Sánchez-Ruiz, J. (2025) Hurricane-induced changes in mayfly assemblage structure, production and emergence in a tropical island stream. Ecological Entomology, 50(1), 201–213. Available from: https:// doi.org/10.1111/een.13394 HURRICANE-INDUCED CHANGES IN MAYFLY ASSEMBLAGES 213 13652311, 2025, 1, D ow nloaded from https://resjournals.onlinelibrary.w iley.com /doi/10.1111/een.13394 by M ontana State U niversity L ibrary, W iley O nline L ibrary on [27/01/2025]. See the T erm s and C onditions (https://onlinelibrary.w iley.com /term s-and-conditions) on W iley O nline L ibrary for rules of use; O A articles are governed by the applicable C reative C om m ons L icense https://doi.org/10.1111/een.13394 https://doi.org/10.1111/een.13394 Cambios inducidos por los huracanes en la estructura, producción, y emergencia del ensamblaje de Ephemeroptera de una quebr... Abstract INTRODUCTION MATERIALS AND METHODS Study site Hurricane history at the LEF Environmental variables Mayfly assemblages Statistical analysis RESULTS Hurricane impacts Assemblages and temporal trends Past hurricanes and emergence DISCUSSION Long‐term hurricane impacts AUTHOR CONTRIBUTIONS ACKNOWLEDGEMENTS CONFLICT OF INTEREST STATEMENT DATA AVAILABILITY STATEMENT ORCID REFERENCES