Terrestrial Adults Research Articles

Exposure to glucocorticoids alters life history strategies in a facultatively paedomorphic salamander.

Polyphenisms, where two or more alternative, environmentally-cued phenotypes are produced from the same genotype, arise through variability in the developmental rate and timing of phenotypic traits. Many of these developmental processes are controlled or influenced by endogenous hormones, such as glucocorticoids, which are known to regulate a wide array of vertebrate ontogenetic transitions. Using the mole salamander, Ambystoma talpoideum, as a model, we investigated the role of glucocorticoids in regulating facultative paedomorphosis, an ontogenetic polyphenism where individuals may delay metamorphosis into terrestrial adults. Instead, individuals reproduce as aquatic paedomorphic adults. Paedomorphosis often occurs when aquatic conditions remain favorable, while metamorphosis typically occurs in response to deteriorating or "stressful" aquatic conditions. Since glucocorticoids are central to the vertebrate stress response and are known to play a central role in regulating obligate metamorphosis in amphibians, we hypothesized that they are key regulators of paedomorphic life history strategies. To test this hypothesis, we compared development of larvae in outdoor mesocosms exposed to Low, Medium, and High exogenous doses of corticosterone (CORT). Results revealed that body size and the proportion of paedomorphs were both inversely proportional to exogenous CORT doses and whole-body CORT content. Consistent with known effects of CORT on obligate metamorphosis in amphibians, our results link glucocorticoids to ontogenetic transitions in facultatively paedomorphic salamanders. We discuss our results in the context of theoretical models and the suite of environmental cues known to influence facultative paedomorphosis.

Trait–environment relationships could alter the spatial and temporal characteristics of aquatic insect subsidies at the macrospatial scale

Ecological flows across ecosystem boundaries are typically studied at spatial scales that limit our understanding of broad geographical patterns in ecosystem linkages. Aquatic insects that metamorphose into terrestrial adults are important resource subsidies for terrestrial ecosystems. Traits related to their development and dispersal should determine their availability to terrestrial consumers. Here, we synthesize geospatial, aquatic biomonitoring and biological traits data to quantify the relative importance of several environmental gradients on the potential spatial and temporal characteristics of aquatic insect subsidies across the contiguous United States. We found the trait composition of benthic macroinvertebrate communities varies among hydrologic regions and could affect how aquatic insects transport subsidies as adults. Further, several trait–environment relationships were underpinned by hydrology. Large bodied taxa that could disperse further from the stream were associated with hydrologically stable conditions. Alternatively, hydrologically variable conditions were associated with multivoltine taxa that could extend the duration of subsidies with periodic emergence events throughout the year. We also found that anthropogenic impacts decrease the frequency of individuals with adult flight but potentially extend the distance subsidies travel into the terrestrial ecosystem. Collectively, these results suggest that natural and anthropogenic gradients could affect aquatic insect subsidies by changing the trait composition of benthic macroinvertebrate communities. The conceptual framework and trait–environment relationships we present shows promise for understanding broad geographical patterns in linkages between ecosystems.

EMERGENCE TRAP FOR THE COLLECTION OF EXUVIAE AND ADULT OF ODONATA

Odonates have aquatic larval stages and terrestrial adults. The extreme change in habitat occupation during their life cycle means that combined collection methods, capable of providing data for both larvae and adults, are scarce and are often inefficient. Given this, we applied a method for the collection of specimens of both life phases using emergence traps. During fieldwork, 78 emergence events were recorded for 15 species. We also briefly discuss the emergence pattern of the recorded species. We believe the information obtained here provide an important contribution to the understanding of the ecology and basic biology of Neotropical odonate species, as well as helping to solve the taxonomic problems associated with the identification of larvae.

Reconciling larval and adult sampling methods to model growth across life-stages.

Individual growth rates are intrinsically related to survival and lifetime reproductive success and hence, are key determinants of population growth. Efforts to quantify age-size relationships are hampered by difficulties in aging individuals in wild populations. In addition, species with complex life-histories often show distinct shifts in growth that cannot be readily accommodated by traditional modelling techniques. Amphibians are often characterized by rapid larval growth, cessation of growth prior to metamorphosis, and resumption of growth in the adult stage. Compounding issues of non-linear growth, amphibian monitoring programs typically sample larval and adult populations using dissimilar methods. Here we present the first multistage growth model that combines disparate data collected across life-history stages. We model the growth of the endangered Reticulated Flatwoods Salamander, Ambystoma bishopi, in a Bayesian framework, that accounts for unknown ages, individual heterogeneity, and reconciles dip-net and drift fence sampling designs. Flatwoods salamanders achieve 60% of growth in the first 3 months of life but can survive for up to 13 years as a terrestrial adult. We find evidence for marked variability in growth rate, the timing and age at metamorphosis, and maximum size, within populations. Average size of metamorphs in a given year appeared strongly dependent on hydroperiod, and differed by >10mm across years with successful recruitment. In contrast, variation in the sizes of emerging metamorphs appeared relatively constant across years. An understanding of growth will contribute to the development of population viability analyses for flatwoods salamanders, will guide management actions, and will ultimately aid the recovery of the species. Our model formulation has broad applicability to amphibians, and likely any stage-structured organism in which homogenous data cannot be collected across life-stages. The tendency to ignore stage-structure or omit non-conforming data in growth analyses can no longer be afforded given the high stakes of management decisions, particularly for endangered or at-risk populations.

Temperature variation magnifies chlorpyrifos toxicity differently between larval and adult mosquitoes

To improve risk assessment there is increasing attention for the effect of climate change on the sensitivity to contaminants and vice versa. Two important and connected topics have been largely ignored in this context: (i) the increase of daily temperature variation (DTV) as a key component of climate change, and (ii) differences in sensitivity to climate change and contaminants between developmental stages. We therefore investigated whether DTV magnified the negative effects of the organophosphate insecticide chlorpyrifos on mortality and heat tolerance and whether this effect was stronger in aquatic larvae than in terrestrial adults of the mosquito Culex pipiens. Exposure to chlorpyrifos at a constant temperature imposed mortality and reduced the heat tolerance in both larvae and adult males, but not in adult females. This provides the first evidence that the TICS (“toxicant-induced climate change sensitivity”) concept can be sex-specific. DTV had no direct negative effects. Yet, consistent with the CITS (“climate-induced toxicant sensitivity”) concept, DTV magnified the toxicity of the pesticide in terms of larval mortality. This was not the case in the adult stage indicating the CITS concept to be dependent on the developmental stage. Notably, chlorpyrifos reduced the heat tolerance of adult females only in the presence of DTV, thereby providing support for the reciprocal effects between DTV and contaminants, hence the coupling of the TICS and CITS concepts. Taken together, our results highlight the importance of integrating DTV and the developmental stage to improve risk assessment of contaminants under climate change.

Stream Mesocosm Experiments Show Significant Differences in Sensitivity of Larval and Emerging Adults to Metals.

Evaluations of aquatic insect responses to contaminants typically use larval life stages to characterize taxa sensitivity, but the effects of contaminants to emerging terrestrial adults have received less attention. We present the results of two stream mesocosm experiments that exposed aquatic insects to mixtures of Cu and Zn. We compared responses of larvae and emerging adults in a single-species experiment with the mayfly Rhithrogena robusta and a benthic community experiment. Results showed that R. robusta larvae and emerging adults were highly tolerant of metals. In the benthic community experiment, larval and emerging adult life stages of the mayfly Baetidae were highly sensitive to metals exposure, with significant alterations in adult sex ratios. In contrast, the emergence of Chironomidae (midge) was unaffected, but larval abundance strongly decreased. Timing of adult emergence was significantly different among treatments and varied among taxa, with emergence stimulation in Chironomidae and delays in emergence in R. robusta and Simuliidae (black fly). Our results demonstrate that metal tolerance in aquatic insects is life stage dependent and that taxa sensitivity is influenced by a combination of physiology and phylogeny. Regulatory frameworks would benefit by including test results that account for effects of contaminants on metamorphosis and adult insect emergence for the development of aquatic life standards.

Ecological and Societal Services of Aquatic Diptera.

More than any other group of macro-organisms, true flies (Diptera) dominate the freshwater environment. Nearly one-third of all flies—roughly 46,000 species—have some developmental connection with an aquatic environment. Their abundance, ubiquity, and diversity of adaptations to the aquatic environment position them as major drivers of ecosystem processes and as sources of products and bioinspiration for the benefit of human society. Larval flies are well represented as ecosystem engineers and keystone species that alter the abiotic and biotic environments through activities such as burrowing, grazing, suspension feeding, and predation. The enormous populations sometimes achieved by aquatic flies can provide the sole or major dietary component for other organisms. Harnessing the services of aquatic Diptera for human benefit depends on the ingenuity of the scientific community. Aquatic flies have played a role as indicators of water quality from the earliest years of bioassessment. They serve as indicators of historical and future ecological and climate change. As predators and herbivores, they can serve as biological control agents. The association of flies with animal carcasses in aquatic environments provides an additional set of tools for forensic science. The extremophilic attributes of numerous species of Diptera offer solutions for human adaptation to harsh terrestrial and extraterrestrial environments. The potential pharmaceutical and industrial applications of the symbiotic microbial community in extremophilic Diptera are better explored than are those of dipteran chemistry. Many flies provide valuable ecological and human services as aquatic immatures, but are also pests and vectors of disease agents as terrestrial adults. The scientific community, thus, is challenged with balancing the benefits and costs of aquatic Diptera, while maintaining sustainable populations as more species face extinction.

DNA barcoding of Sialis sp. (Megaloptera) in Portugal: the missing tool to species identification

DNA barcoding is increasingly used to identify species in a rapid and automated way, and may be particularly useful for morphologically similar larvae of aquatic insects. Identification of aquatic larvae of the alderfly genus Sialis Latreille, 1803 is troublesome due to limited morphological characters, though terrestrial adults are readily identifiable morphologically. This greatly limits our understanding of Sialis distribution and ecology, as adults are generally difficult to find and collect. In Portugal, only Sialis fuliginosa Pictet, 1836 has been previously collected, but there are numerous records of unidentified Sialis larvae. Based on morphology and DNA barcoding of the adult specimens recently collected in the country, we confirmed the presence of S. fuliginosa and in addition detected S. lutaria Linnaeus, 1758 and S. nigripes Pictet, 1865, which are reliably reported from Portugal for the first time. We found that DNA barcodes can unequivocally distinguish the three species, providing a basis to identify larval stages in future ecological and monitoring studies.

Delayed effects and complex life cycles: How the larval aquatic environment influences terrestrial performance and survival.

Species with complex life cycles are susceptible to environmental stressors across life stages, but the carryover and latent effects between stages remain understudied. For species with biphasic life histories, such as pond-breeding amphibians, delayed effects of aquatic conditions can influence terrestrial juveniles and adults directly or indirectly, usually mediated through fitness correlates such as body size. We collected adult southern toads (Anaxyrus terrestris) from 2 source populations-a natural reference wetland and a metal-contaminated industrial wetland-and exposed their offspring to 2 aquatic stressors (a metal contaminant, copper [Cu], and a dragonfly predator cue) in outdoor mesocosms (n = 24). We then reared metamorphs in terraria for 5 mo to examine delayed effects of early life stage environmental conditions on juvenile performance, growth, and survival. Larval exposure to Cu, as well as having parents from a contaminated wetland, resulted in smaller size at metamorphosis-a response later negated by compensatory growth. Although Cu exposure and parental source did not affect larval survival, we observed latent effects of these stressors on juvenile survival, with elevated Cu conditions and metal-contaminated parents reducing postmetamorphic survival. Parental source and larval Cu exposure affected performance at metamorphosis through carryover effects on body size but, 1 mo later, latent effects of parental source and larval predator exposure directly (i.e., not via body size) influenced performance. The carryover and latent effects of parental source population and aquatic Cu level on postmetamorphic survival and juvenile performance highlight the importance of conducting studies across life stages and generations. Environ Toxicol Chem 2018;37:2660-2669. © 2018 SETAC.

Severing Ties: Different Responses of Larval and Adult Aquatic Insects to Atrazine and Selenium

Aquatic insects link aquatic and terrestrial ecosystems through their metamorphosis and subsequent transition from water to land. Chemical stressors in freshwater, such as agricultural contaminants, can potentially disrupt insect life cycles and reduce the number of insects emerging as terrestrial adults, thereby damaging or severing this linkage. Atrazine and selenium, though frequently detected in waterways and often co-occurring, have not been previously studied together in controlled experiments. We conducted a six-week mesocosm experiment to measure the responses of larval and emerging aquatic insects to treatments of atrazine (15 μg/L), selenium (10 μg/L), and a direct combination of the two. Peak adult insect abundance was reduced in all treatments by 35% to 45% relative to the control. Further, cumulative adult emergence in the combined treatment was 33% lower than in the control. However, no reductions in primary production were observed with treatments, and consistent reductions in benthic insect abundance relative to the control were not observed until the end of the experiment, when overall abundance was low. Results suggest that adult insects are more sensitive than larval insects to atrazine and selenium and that the impacts of these contaminants are stronger on the terrestrial than the aquatic ecosystem.

Comparative expression analysis identifies the respiratory transition-related miRNAs and their target genes in tissues of metamorphosing Chinese giant salamander (Andrias davidianus)

BackgroundChinese giant salamander (Andrias davidianus) undergoes a metamorphosis from aquatic larvae to terrestrial adults, with concomitant transfer of respiration from gills to lungs prior to metamorphosis. These two tissues, as well as skin, were sampled to identify the differentially expressed miRNAs.ResultsHigh-coverage reference transcriptome was generated from combined gill, lung and skin tissues of metamorphosing juveniles, and lung tissue of adults: 86,282 unigenes with total length of approximately 77,275,634 bp and N50 of 1732 bp were obtained. Among these, 13,246 unigenes were assigned to 288 pathways. To determine the possible involvement of miRNAs in the respiratory transition, small RNA libraries were sequenced; 282 miRNAs were identified, 65 among which were known and 217 novel. Based on the hierarchical clustering analysis, the twelve studied samples were classified into three major clusters using differentially expressed miRNAs. We have validated ten differentially expressed miRNAs and some of their related target genes using qPCR. These results largely corroborated the results of transcriptomic and miRNA analyses. Finally, an miRNA-gene-network was constructed. Among them, two miRNAs with target genes related to oxygen sensing were differentially expressed between gill and lung tissues. Three miRNAs were differentially expressed between the lungs of larvae and lungs of adults.ConclusionsThis study provides the first large-scale miRNA expression profile overview during the respiration transition from gills to lungs in Chinese giant salamander. Five differentially expressed miRNAs and their target genes were identified among skin, gill and lung tissues. These results suggest that miRNA profiles in respiratory tissues play an important role in the regulation of respiratory transition.

Extreme streams: species persistence and genomic change in montane insect populations across a flooding gradient.

The ecological and evolutionary consequences of extreme events are poorly understood. Here, we tested predictions about species persistence and population genomic change in aquatic insects in 14 Colorado mountain streams across a hydrological disturbance gradient caused by a one in 500-year rainfall event. Taxa persistence ranged from 39 to 77% across sites and declined with increasing disturbance in relation to species' resistance and resilience traits. For taxa with mobile larvae and terrestrial adult stages present at the time of the flood, average persistence was 84% compared to 25% for immobile taxa that lacked terrestrial adults. For two of six species analysed, genomic diversity (allelic richness) declined after the event. For one species it greatly expanded, suggesting resilience via re-colonisation from upstream populations. Thus, while resistance and resilience traits can explain species persistence to extreme disturbance, population genomic change varies among species, challenging generalisations about evolutionary responses to extreme events at landscape scales.

Carry-Over Effects Across Metamorphosis of a Pesticide on Female Lifetime Fitness Strongly Depend on Egg Hatching Phenology: A Longitudinal Study under Seminatural Conditions

Current ecological risk assessment of pesticides fails to protect aquatic biodiversity. For the first time, we tested two potential reasons for this failure with regard to carry-over effects across metamorphosis: their dependence on hatching period, and the lack of studies quantifying adult fitness under seminatural conditions. Using the damselfly Coenagrion puella sampled from six populations, we designed an outdoor longitudinal one-year study starting from the egg stage. We exposed the aquatic larvae to the pesticide esfenvalerate (0.11 μg/L) during the initial microcosm part. Next, we monitored the lifetime fitness of the terrestrial adults in an insectary. Exposure to the pesticide negatively impacted not only larval traits, but also drastically reduced lifetime mating success of adult females. The impact of this postmetamorphic effect of the pesticide on the population level was three times more important than the effects in the larval stage. Importantly, this carry-over effect was only present in females that hatched early in the season, and was not mediated by metamorphic traits (age and mass at emergence). We provide proof-of-principle under seminatural conditions for two potential pitfalls that need to be considered when improving risk assessment: carry-over effects on adult fitness can (i) be much more important than effects during the larval stage and may not be captured by metamorphic traits, and (ii) be strongly modulated by egg hatching dates.

First records of adult feeding in Megaloptera (Corydalidae, Corydalinae) from Mexico and their possible relationship with the increase in life span.

Knowledge of the natural history of the order Megaloptera is incomplete. Immatures are long-lived and widely known for their role as aquatic predators (Contreras-Ramos 1998; Azevêdo & Hamada 2007), yet information on habits of the winged terrestrial adults is limited. Previously, it was thought that adults do not feed (Table 1), perhaps because of the relatively short life span of about one week to a month (Contreras-Ramos 1998, 1999; Hayashi 1993), as well as the inability of males of Corydalus Latreille, 1802 to feed due to their large mandibles. Tierno de Figueroa & Palomino (2002) analyzed the digestive tract of Sialis nigripes Pictet, 1865 in Spain, and found debris and a spermatophore in a female. Also, Contreras-Ramos (1999) recorded the acceptance of sugar water by adults of Platyneuromus soror (Hagen, 1861). However, consumption of solid organic matter in adult Megaloptera has not previously been recorded.

The ontogeny of the olfactory system in ceratophryid frogs (Anura, Ceratophryidae).

The aquatic-to-terrestrial shift in the life cycle of most anurans suggests that the differences between the larval and adult morphology of the nose are required for sensory function in two media with different physical characteristics. However, a better controlled test of specialization to medium is to compare adult stages of terrestrial frogs with those that remain fully aquatic as adults. The Ceratophryidae is a monophyletic group of neotropical frogs whose diversification from a common terrestrial ancestor gave rise to both terrestrial (Ceratophrys, Chacophrys) and aquatic (Lepidobatrachus) adults. So, ceratophryids represent an excellent model to analyze the morphology and possible changes related to a secondary aquatic life. We describe the histomorphology of the nose during the ontogeny of the Ceratophryidae, paying particular attention to the condition in adult stages of the recessus olfactorius (a small area of olfactory epithelium that appears to be used for aquatic olfaction) and the eminentia olfactoria (a raised ridge on the floor of the principal cavity correlated with terrestrial olfaction). The species examined (Ceratophrys cranwelli, Chacophrys pierottii, Lepidobatrachus laevis, and L. llanensis) share a common larval olfactory organ composed by the principal cavity, the vomeronasal organ and the lateral appendix. At postmetamorphic stages, ceratophryids present a common morphology of the nose with the principal, middle, and inferior cavities with characteristics similar to other neobatrachians at the end of metamorphosis. However, in advanced adult stages, Lepidobatrachus laevis presents a recessus olfactorius with a heightened (peramorphic) development and a rudimentary (paedomorphic) eminentia olfactoria. Thus, the adult nose in Lepidobatrachus laevis arises from a common developmental 'terrestrial' pathway up to postmetamorphic stages, when its ontogeny leads to a distinctive morphology related to the evolutionarily derived, secondarily aquatic life of adults of this lineage.

Pollination system of Corylopsis gotoana (Hamamelidaceae) and its stonefly (Plecoptera) co‐pollinator

AbstractThe order Plecoptera is primarily known for its aquatic nymphs and their importance in many stream ecosystems. However, the biology and life history of Plecopteran terrestrial adults is mostly unknown, and hence interactions with plants have rarely been documented. Here, we report on insect visitation to flowers of Corylopsis gotoana (Hamamelidaceae) in a temperate forest of Japan, with emphasis on the behavior and pollination role of adults of a stonefly species, Strophopteryx nohirae (Taeniopterygidae), which were frequently observed in the flowers. The most frequent insect visitors to Corylopsis flowers were Bombylius major (Bombyliidae), Apis cerana (Apidae) and Bombus ardens (Apidae), all of which were considered main pollinators because of high rates of visitation and pollen attachment. Strophopteryx nohirae frequently visited Corylopsis trees, on which they foraged for pollen and mated. A field experiment on the pollination success of Corylopsis flowers visited by S. nohirae verified that this stonefly contributed to pollination.

Mosquito female response to the presence of larvivorous fish does not match threat to larvae

1. Several species with complex life‐history traits such as amphibians and insects with aquatic immature stages and terrestrial adults avoid ovipositing in pools containing larvivorous fish. This avoidance response was assumed to be a general one for most fish species.2. The generality of ovipositing Culex to the presence of three, widespread larvivorous fish species was tested in a set of field experiments with artificial oviposition pools using caged fish.3. Larval performance was further examined under actual predation by these three fish species.4. Results show that ovipositing females responded strongly to the presence of caged mosquitofish, Gambusia affinis, while showing no significant response to the presence of caged green sunfish, Lepomis cyanellus, or the pirate perch, Aphredoderus sayanus. All three fish species consumed similar amounts of larvae.5. This is the first example of species‐specific response differences to predators during mosquito oviposition habitat selection. These results point to the existence of predator‐released kairomones affecting mosquito behaviour. These kairomones may either be species‐specific or vary in concentration among fish, and probably have an important role in the understanding of mosquito spatial distribution.

Acoustic orientation in the great crested newt (Triturus cristatus)

We carried out laboratory experiments to determine whether orientation during migration in the great crested newt (Triturus cristatus) is influenced by acoustic information. Newts retrieved during the aquatic breeding seasons (adults), as well as during the terrestrial phase after breeding (adults and juveniles), were subjected to calls from sympatric (Rana temporariaandBufo bufo) and allopatric (Lithobates catesbeianus) anurans. In addition to natural stimuli, we also used modified anuran calls (continuous sound with inter-note intervals removed), white noise with and without envelop, and a heterochthonous sound (pile driving). In a circular arena, adult newts retrieved both during their aquatic and terrestrial phase orientated towards theB. bufostimulus, and migrated at random directions when exposed to the other calls; the lack of orientation towards the sympatricR. temporariaparallels a largely non-overlapping breeding season. Inexperienced juveniles did not orientate towards anuran calls, suggesting that phonotactic responses could be learned. Both aquatic as well as terrestrial adults significantly moved away from a white noise envelop. The results suggest different degrees of heterospecific call attraction across life stages, and provide evidence that unnatural sound might have an adverse effect on breeding migrations.

Multiple major histocompatibility complex class I genes in Asian anurans: Ontogeny and phylogeny

Amphibians, as the first terrestrial vertebrates, offer a window into early major histocompatibility complex (MHC) evolution. We characterized the MHC class I of two Korean amphibians, the Asiatic toad (Bufo gargarizans) and the Japanese tree frog (Hyla japonica). We found at least four transcribed MHC class I (MHC I) loci, the highest number confirmed in any anuran to date. Furthermore, we identified MHC I transcripts in terrestrial adults, and possibly in aquatic larvae, of both species. We conducted a phylogenetic analysis based on MHC I sequence data and found that B. gargarizans and H. japonica cluster together in the superfamily Nobleobatrachia. We further identified three supertypes shared by the two species. Our results reveal substantial variation in the number of MHC I loci in anurans and suggest that certain supertypes have particular physiochemical properties that may confer pathogen resistance.

A fresh approach reveals how dispersal shapes metacommunity structure in a human‐altered landscape

Summary To understand species losses from disturbed landscapes, it is important to distinguish the effects of degraded environmental conditions from those caused by barriers to dispersal between habitat patches. To assess the relative importance of these effects, we developed a new approach using permutation and association tests applied to rank abundance data, using the invertebrate fauna of two rivers in two seasons. Our study streams were Hughes Creek and Seven Creeks, in south‐eastern Australia, which have both been degraded by agriculture in downstream sections. We collected benthic invertebrates and also dispersing individuals (drift, terrestrial adults) during two seasons in 2007–2008. Study sites spanned strong environmental gradients as well as the main dispersal route (up‐ and down‐channel). Environmental data were analysed to set up permutation tests on rank abundances. Survey and disperser data were contrasted using contingency table analyses. The results suggest dispersal plays a strong role in community structure. Environmental effects were evident and strongest upstream, but evidence of environmental effects was weak over much of the gradient. Many species had different distributions in different data sets or dispersers that were abundant at locations distant from centres of benthic distribution. Our results differ from many studies, but few have been able to evaluate dispersal effects directly. Our method provides a practical approach for evaluating the role dispersal plays in driving species abundance patterns across landscapes, thus bridging a gap between theory and practice. Synthesis and applications. Managers typically use indices of ecosystem health that assume environmental conditions largely determine species diversity and abundance. Dispersal between habitat patches is known to be important, but there are no reliable methods to assess the role dispersal may play. We provide an approach that allows both dispersal and environmental effects on species distributions to be evaluated from survey data. This may open the way for dispersal information to be incorporated into management actions. Additionally, the approach should allow improved siting of restoration projects that depend greatly on successful dispersal of individuals for successful outcomes.