Similar Life History Strategies Research Articles

Rapid growth in Late Cretaceous sea turtles reveals life history strategies similar to extant leatherbacks.

Modern sea turtle long bone osteohistology has been surprisingly well-studied, as it is used to understand sea turtle growth and the timing of life history events, thus informing conservation decisions. Previous histologic studies reveal two distinct bone growth patterns in extant sea turtle taxa, with Dermochelys (leatherbacks) growing faster than the cheloniids (all other living sea turtles). Dermochelys also has a unique life history compared to other sea turtles (large size, elevated metabolism, broad biogeographic distribution, etc.) that is likely linked to bone growth strategies. Despite the abundance of data on modern sea turtle bone growth, extinct sea turtle osteohistology is virtually unstudied. Here, long bone microstructure of the large, Cretaceous sea turtle Protostega gigas is examined to better understand its life history. Humeral and femoral analysis reveals bone microstructure patterns similar to Dermochelys with variable but sustained rapid growth through early ontogeny. Similarities between Progostegea and Dermochelys osteohistology suggest similar life history strategies like elevated metabolic rates with rapid growth to large body size and sexual maturity. Comparison to the more basal protostegid Desmatochelys indicates elevated growth rates are not present throughout the entire Protostegidae, but evolved in larger and more derived taxa, possibly in response to Late Cretaceous ecological changes. Given the uncertainties in the phylogenetic placement of the Protostegidae, these results either support convergent evolution towards rapid growth and elevated metabolism in both derived protostegids and dermochelyids, or a close evolutionary relationship between the two taxa. Better understanding the evolution and diversity of sea turtle life history strategies during the Late Cretaceous greenhouse climate can also impact current sea turtle conservation decisions.

Can sea snakes slither through seascape structure? Comparative phylogeography and population genetics of Hydrophis group sea snakes in Australia and Southeast Asia

Pleistocene sea level changes substantially shaped the biogeography of northern Australia and the Indo-Malayan Archipelago (IMA). For co-distributed species, their phylogeographic and population genetic patterns are expected to be concomitant with geological transformations of the Pleistocene. However, species-specific ecologies and life history traits may also be influential in generating patterns which depart from simple expectations arising from biogeographic features. Thus, comparative population genetic studies, which use taxa that reduces variation in taxonomy and geography, may refine our understanding of how biogeographic elements shape the populations of co-occurring species. Here, we sampled two sea snake species, Hydrophis curtus and H. elegans, throughout their known ranges in the IMA and northern Australia. These sea snakes have similar life history strategies and ecologies as well as overlapping distributions across the Torres Strait, a well-known biogeographic feature. We analysed two mitochondrial DNA (mtDNA) fragments and 10 microsatellite loci using traditional population genetic approaches and used Bayesian clustering methods to examine species- specific phylogenetic relationships, genetic diversities, and population genetic structures. For both species, we found a consistent lack of significant genetic variation among sampling sites across the Gulf of Carpentaria (GOC) and the Great Barrier Reef (GBR). Similarly, Bayesian clustering showed no to weak genetic partitioning across the historical Torres Strait land bridge. Both species sampled in Australia displayed population expansion signatures in tests using mtDNA and microsatellite markers. We conclude that the phylogeographic and population genetic patterns of these sea snake species do not align with the Torres Strait land bridge. This lack of population genetic structure departs from previous findings on Aipysurus sea snakes and may be linked to the association of Hydrophis species to soft sediment habitats typically found across northern Australia. These divergent patterns between the sea snake groups present the importance of considering taxon-specific attributes in formulating conservation strategies.

Multituberculate Mammals Show Evidence of a Life History Strategy Similar to That of Placentals, Not Marsupials.

AbstractThe remarkable evolutionary success of placental mammals has been partly attributed to their reproductive strategy of prolonged gestation and birthing of relatively precocial, quickly weaned neonates. Although this strategy was conventionally considered derived relative to that of marsupials with highly altricial neonates and long lactation periods, mounting evidence has challenged this view. Until now the fossil record has been relatively silent on this debate, but here we find that proportions of different bone tissue microstructures in the femoral cortices of small extant marsupials and placentals correlate with length of lactation period, allowing us to apply this histological correlate of reproductive strategies to Late Cretaceous and Paleocene members of Multituberculata, an extinct mammalian clade that is phylogenetically stemward of Theria. Multituberculate bone histology closely resembles that of placentals, suggesting that they had similar life history strategies. A stem-therian clade exhibiting evidence of placental-like life histories supports the hypothesis that intense maternal-fetal contact characteristic of placentals is ancestral for therians. Alternatively, multituberculates and placentals may have independently evolved prolonged gestation and abbreviated lactation periods. Our results challenge the hypothesis that the rise of placental mammals was driven by unique life history innovations and shed new light on early mammalian diversification.

Advancements in the Understanding of Appalachian Primary Burrowing Crayfish Ecology and Habitat Usage with a Focus on Cambarus monongalensis

Primary burrowing crayfish life history and ecology is largely due to their cryptic habitat preferences. Cambarus monongalensis, arguably the most charismatic of all crayfishes, lacks basic life history and habitat data because of the aforementioned obstacles. This study seeks to determine the life history and ecological preferences of populations of C. monongalensis in the northern panhandle of West Virginia and Southwestern Pennsylvania with notes on its natural history. Life history data will include form change and reproductive patterns including juvenile size of departure from the maternal burrow. Habitat data were collected using external burrow morphology and burrow locations within a standardized area collected seasonally to determine the preferences and cyclical patterns of crayfishes. With these data, the conservation of this species, and others that follow a similar life history strategy, is possible

An investigation of genetic connectivity shines a light on the relative roles of isolation by distance and oceanic currents in three diadromous fish species

Understanding connectivity is crucial for the effective conservation and management of biota. However, measuring connectivity directly is challenging and it is often inferred based on assumptions surrounding dispersal potential, such as environmental history and species life history traits. Genetic tools are often underutilised, yet can infer connectivity reliably. Here, we characterise and compare the genetic connectivity and genetic diversity of three diadromous Australian fish species: common galaxias (Galaxias maculatus), tupong (Pseudaphritis urvillii) and Australian grayling (Prototroctes maraena). For each species, we investigate the extent of genetic connectivity across a study region in south-eastern Australia (~700 km). We further determine the potential roles of contemporary ocean currents in shaping the patterns of genetic connectivity observed. Individuals across multiple rivers were sampled and >3000 single nucleotide polymorphisms were genotyped for each species. We found differences in genetic connectivity for the three species: common galaxias were highly connected, and Australian grayling and tupong exhibited patterns of isolation by distance. The degree of genetic connectivity for tupong and Australian grayling appeared unrelated to oceanic currents. This study indicates that the degree of connectivity for different diadromous species can vary greatly despite broadly similar life history strategies, highlighting the potential value of genetic tools for informing species-specific management plans.

Preimaginal developmental time of two egg parasitoids and their host searching efficiency

ABSTRACTWhen searching for hosts, parasitoids may experience competition between adults exploiting the same host (extrinsic), or between larvae developing inside the host (intrinsic competition). Differences in competitive abilities like host location and resource utilisation promote coexistence. In this sense, extrinsically superior parasitoids better locate hosts, and intrinsically superior ones can have a shorter preimaginal development, which gives them a competitive advantage in physiological suppression against its competitor. Piezodorus guildinii (Hemiptera: Pentatomidae) is an important soybean pest, and its main natural enemies are egg parasitoids Telenomus podisi and Trissolcus urichi (Hymenoptera: Platygastridae). We compared the ability of wasps to locate host eggs, and larval development time of both parasitoids. Both species took the same amount of time to find and contact eggs, and to start parasitising them. There were no differences in average development time of larvae, pupae, and the entire preimaginal period. Both parasitoid species compared in this study are closely related, having very similar life history strategies. These factors could have covered up other aspects of the host foraging abilities of each species, which can make differences between them when searching for hosts in the field. Moreover, searching abilities of both species could be similar under laboratory conditions but different under field conditions. Understanding competitive interactions between parasitoids is important to improve the biological control of the pest.

Comparative genomic analysis of three co-occurring annual Asteraceae along micro-geographic fragmentation scenarios

This is the first population genomic analysis that examines micro-evolutionary changes in co-occurring plant species, in fragmented habitats, along a precipitation gradient. We applied Genotype-by-Sequencing (GBS) on three different annual Asteraceae on the same sites that share similar life history strategies, but different pollination and dispersal strategies (Catananche lutea, Geropogon hybridus, Urospermum picroides).We tested if the genetic diversity for all species correlates with effective population sizes along the precipitation gradient and whether therefore genetic drift drives evolution at range edges. However, our results support this hypothesis for only one species (C. lutea) but refute it for the other two. Potential genomic signals of adaptation to the high precipitation gradient were found only in one species (U. picroides). We also tested if species with complex pollination and diversified dispersal strategies are less affected by small scale habitat fragmentation, but the opposite is true. Biological differences between the species studied (pollination and dispersal) explain population genetic differences along the precipitation gradient at range edges rather than environmental filters. Pairwise correlation analyses showed no or only weak similarities in the accumulation of mutations in the different species.Our results suggest that the processes driving evolution in different co-occurring species are different, so that most genomic similarities in our investigations may only represent temporary stages in evolution.

Animal life history is shaped by the pace of life and the distribution of age-specific mortality and reproduction.

Animals exhibit an extraordinary diversity of life history strategies. These realized combinations of survival, development and reproduction are predicted to be constrained by physiological limitations and by trade-offs in resource allocation. However, our understanding of these patterns is restricted to a few taxonomic groups. Using demographic data from 121 species, ranging from humans to sponges, we test whether such trade-offs universally shape animal life history strategies. We show that, after accounting for body mass and phylogenetic relatedness, 71% of the variation in animal life history strategies can be explained by life history traits associated with the fast-slow continuum (pace of life) and with a second axis defined by the distribution of age-specific mortality hazards and the spread of reproduction. While we found that life history strategies are associated with metabolic rate and ecological modes of life, surprisingly similar life history strategies can be found across the phylogenetic and physiological diversity of animals.

Short-term population dynamics of Helianthemum caput-felis, a perennial Mediterranean coastal plant: a key element for an effective conservation programme

Plant population dynamics is fundamental to identify which parts of the life cycle are important when designing management actions. In this study, the short-term population dynamics of Helianthemum caput-felis (Cistaceae), a perennial plant distributed throughout the western Mediterranean Basin, was investigated by monitoring 98 permanent plots randomly placed along the overall distribution range for three years (2013–2015). Demographic surveys were analysed by Integral Projection Models (IPMs), and the analysis of population growth rates, elasticities, and life table response experiment (LTRE) analyses were performed. Under deterministic conditions, the H. caput-felis population showed a slight increase in the first censuses, but a general population decline followed. This trend was probably due to the shrinkage of plants in the last year, which correlated negatively with reproductive traits. Despite this decline, the population was at equilibrium under the simulated environmental stochasticity. The population dynamics of H. caput-felis followed the general pattern typical for long-lived Mediterranean plants: populations with growth rates closer to the equilibrium in the long term, determinant role of the survival-growth transitions for the population growth rate, slow growth and stasis, longevity of established individuals, shrinkage of medium-large plants, low recruitment rate, high generation times and mean long lifespans. The results of this study, which highlight how conservation measures can be focused on protecting and increasing the number of plants of medium-large size, provide important information for the planning management conservation actions for H. caput-felis and for several Mediterranean plants that show a similar life-history strategy.

Closely related octopus species show different spatial genetic structures in response to the Antarctic seascape.

Determining whether comparable processes drive genetic divergence among marine species is relevant to molecular ecologists and managers alike. Sympatric species with similar life histories might be expected to show comparable patterns of genetic differentiation and a consistent influence of environmental factors in shaping divergence. We used microsatellite loci to quantify genetic differentiation across the Scotia Arc in three species of closely related benthic octopods, Pareledone turqueti, P. charcoti, and Adelieledone polymorpha. The relative importance of environmental factors (latitude, longitude, depth, and temperature) in shaping genetic structure was investigated when significant spatial genetic structure was uncovered. Isolated populations of P. turqueti and A. polymorpha at these species’ range margins were genetically different to samples close to mainland Antarctica; however, these species showed different genetic structures at a regional scale. Samples of P. turqueti from the Antarctic Peninsula, Elephant Island, and Signy Island were genetically different, and this divergence was associated primarily with sample collection depth. By contrast, weak or nonsignificant spatial genetic structure was evident across the Antarctic Peninsula, Elephant Island, and Signy Island region for A. polymorpha, and slight associations between population divergence and temperature or depth (and/or longitude) were detected. Pareledone charcoti has a limited geographic range, but exhibited no genetic differentiation between samples from a small region of the Scotia Arc (Elephant Island and the Antarctic Peninsula). Thus, closely related species with similar life history strategies can display contrasting patterns of genetic differentiation depending on spatial scale; moreover, depth may drive genetic divergence in Southern Ocean benthos.

Dispersal-limited detritivores in fire-prone environments: persistence and population structure of terrestrial amphipods (Talitridae)

Invertebrate detritivores play a critical role in the decomposition of litter, an important component of wildfire fuel. Knowledge of invertebrate response to fire is often hampered by taxonomic resolution; however, genetic species identification can enable analysis of fine-scale assemblages and the interaction between dispersal and population recovery. In this study, we ask: do terrestrial amphipod assemblages differ following increasing fire severities and does population structure indicate in situ survival or recolonisation following severe fires? Using seven replicate sites over three fire severities, we measured amphipod abundance at the site of the catastrophic 2009 ‘Black Saturday’ fires in south-east Australia. Genetic analyses to distinguish species and population structure revealed 16 species. Populations of Arcitalitrus sylvaticus were highly structured, suggesting limited dispersal. Amphipod abundance and species richness were not affected by fire severity 3 years after fire. Localised population structure within A. sylvaticus suggests that in situ survival enabled amphipods to repopulate severely burnt sites. The genetic analyses used in this study enabled the detection of unrecognised diversity and population structure in these detritivores. With many detritivores showing similar life history strategies, studies that combine a genetic and ecological approach are essential for understanding the impact of fire on litter decomposition.

Comparative reproductive biology of sympatric species: nest and chick survival of American avocets and black‐necked stilts

Identifying differences in reproductive success rates of closely related and sympatrically breeding species can be useful for understanding limitations to population growth. We simultaneously examined the reproductive ecology of American avocets Recurvirostra americana and black‐necked stilts Himantopus mexicanus using 1274 monitored nests and 240 radio‐marked chicks in San Francisco Bay, California. Although there were 1.8 times more avocet nests than stilt nests, stilts nonetheless fledged 3.3 times more chicks. Greater production by stilts than avocets was the result of greater chick survival from hatching to fledging (avocet: 6%; stilt: 40%), and not because of differences in clutch size (avocet: 3.84; stilt: 3.77), nest survival (avocet: 44%; stilt: 35%), or egg hatching success (avocet: 90%; stilt: 92%). We reviewed the literature and confirmed that nest survival and hatching success are generally similar when avocets and stilts breed sympatrically. In addition to species, chick survival was strongly influenced by age, site, and year. In particular, daily survival rates increased rapidly with chick age, with 70% of mortalities occurring ≤ 1 week after hatch. California gulls Larus californicus caused 55% of avocet, but only 15% of stilt, chick deaths. Differential use of micro‐habitats likely reduced stilt chick's vulnerability to gull predation, particularly during the first week after hatch, because stilts nested in vegetation 2.7 times more often than avocets and vegetation height was 65% taller at stilt nests compared with avocet nests. Our results demonstrate that two co‐occurring and closely related species with similar life history strategies can differ markedly in reproductive success, and simultaneous studies of such species can identify differences that limit productivity.

Broad polyphyly and historical biogeography of the neotropical wasp genus Notiospathius (Braconidae: Doryctinae)

Morphological convergence is a frequently observed pattern that occurs in species with similar environments, trophic niches, and/or life history strategies. In particular, adaptive morphological convergence is common in small, highly diverse invertebrate taxa sharing similar life history strategies such as parasitoidism. The genus Notiospathius is a braconid parasitoid wasp group with a vast, undetermined number of species distributed throughout the Neotropics. Members of this genus possess a considerably elongated, petiolate first metasomal tergite. This structure, however, also occurs in species of other doryctine genera, both closely and distantly related, probably due to adaptation for attacking wood and bark boring coleopteran larvae. Here we investigated the phylogenetic relationships among 117 species assigned to Notiospathius, including species of its closely related genera Masonius and Tarasco, as well as members of a number of other doryctine genera in order to test its monophyly. Separate and concatenated Bayesian partitioned analyses were carried out using two mitochondrial and three nuclear gene markers. The influence of each gene on the overall topology was verified using a cross-validation analysis for each marker with a “leave-one-out” approach. Moreover, the historical biogeography of Notiospathius was assessed calculating divergence time estimates of clades with BEAST and performing ancestral area reconstruction analyses both with RASP (Bayesian and S-DIVA) and Lagrange (DEC). All analyses recovered a polyphyletic Notiospathius consisting of three separate clades that were more related to other doryctine genera than to each other. The relationships reconstructed could not be used to confidently establish the limits of Notiospathius with respect to its closely related genera Tarasco and Masonius, and thus the generic status of the latter two taxa is maintained. Our divergence time estimates and ancestral area reconstructions indicate that the most recent common ancestor of Notiospathius sensu stricto originated in the Caribbean subregion during the Oligocene–Miocene boundary, and subsequently diversified during the mid- to late Miocene, radiating throughout the Neotropics.

Competitive Interactions of Garlic Mustard (Alliaria petiolata) and Damesrocket (Hesperis matronalis)

AbstractCompetitive interactions between native plants and nonnative, invasive plant species have been extensively studied; however, within degraded landscapes, the effect of interspecific interactions among invasive plants is less explored. We investigated a competitive interaction between two sympatric, invasive mustard species that have similar life history strategies and growth forms: garlic mustard and damesrocket. Greenhouse experiments using a full range of reciprocal density ratios were conducted to investigate interspecific competition. Garlic mustard had a negative effect on the final biomass, number of leaves, and relative growth rate in height of damesrocket. Survival of damesrocket was not negatively affected by interspecific competition with garlic mustard; however, garlic mustard showed higher mortality because of intraspecific competition. These results indicated that although garlic mustard has been observed to be the dominant species in this landscape, it may not completely outcompete damesrocket in all situations. Studies of invasive species in competition are important in degraded landscapes because this is the common situation in many natural areas.

Reproduction, aging, and body shape by three‐dimensional photonic scanning in Thai men and women

Aging and reproduction have been independently associated with body shape in women, with redistribution of body fat from lower to upper body regions. This may be interpreted as a life history strategy for allocating energy between competing peripheral fat depots for reproduction, and central fat depots for maintenance and survival. It remains unclear whether men show similar life history strategy in shape. The objectives of this study were to investigate associations between shape, age, and number of offspring in both men and women from Thailand. We analyzed data on body shape from three-dimensional photonic scanning, and number of reported offspring, available for 5,889 men and 6,449 women aged 16-90 years from the Thai National Sizing Survey. Bearing children was associated with increased upper body girths and decreased lower body girths in women, independent of age, weight and height. Unlike motherhood, fatherhood was not associated with shape outcomes indexing adiposity, but was associated with arm girth, which may represent an index of sexual attractiveness. In those without children, aging was associated with greater upper body girths and reduced lower body girths, in both sexes. Life history strategy in body shape is apparent in both sexes, with aging associated with a shift of tissue away from the lower limb to the upper body. Such strategy may reflect age-changes in the relative costs and benefits of different regional tissue masses. Changes in fat distribution related to aging and reproduction may contribute to the life-course development of cardiovascular risk.

Five ways to skin a cat: An unexpected diversity of stress profiles in five species of ground squirrels

Event Abstract Back to Event Five ways to skin a cat: An unexpected diversity of stress profiles in five species of ground squirrels Brendan Delehanty1* and Rudy Boonstra1 1 University of Toronto at Scarborough, Biological Sciences, Canada Comparative physiologists often hypothesize that animals facing similar problems will have similar solutions; that is, we expect general patterns to emerge. The alternative hypothesis is that few, if any, patterns will emerge because each species is able to so finely manipulate its physiology that there are any number of ways to solve the same problem. We studied stress axis (hypothalamic-pituitary-adrenal axis) function over the course of the breeding season in a group of closely related ground squirrel species. Because the stress axis is highly conserved among vertebrates in terms of its basic functioning, and because all of the ground squirrel species we studied face similar reproductive challenges (all are hibernators that compete for mating opportunities shortly upon emerging from hibernation), we expected that species sharing similar life history strategies would have similar stress profiles. For each species we obtained pre- and post-breeding stress profiles of males that included stress-induced glucocorticoid (GC) levels, GC levels in response to a hormone challenge protocol (dexamethasone suppression and ACTH stimulation), blood glucose levels, free fatty acids, and complete blood counts. We found that life history did not predict stress profile: each species had a unique stress profile, with no two species sharing even basic trends in GC levels and binding capacity. Trends in total GC concentrations, GC binding capacity, and free GC concentrations over the course of the breeding season varied between all 5 species studied. Moreover, the downstream measures of stress (glucose, free fatty acids, hematocrit, complete blood counts) showed similar variability and could not be predicted from simple measures of GC concentrations. We conclude that many of our simplifying assumptions about how the stress axis supports or constrains reproduction need to be revisited. Acknowledgements Supported by NSERC grant to R.B. and NSTP Grant to B.D. Keywords: downstream effects, Glucocorticoids, ground squirrels, Reproduction, stress profiles Conference: NASCE 2011: The inaugural meeting of the North American Society for Comparative Endocrinology, Ann Arbor, United States, 13 Jul - 16 Jul, 2011. Presentation Type: Poster Topic: Stress hormones Citation: Delehanty B and Boonstra R (2011). Five ways to skin a cat: An unexpected diversity of stress profiles in five species of ground squirrels. Front. Endocrinol. Conference Abstract: NASCE 2011: The inaugural meeting of the North American Society for Comparative Endocrinology. doi: 10.3389/conf.fendo.2011.04.00125 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 20 Jul 2011; Published Online: 09 Aug 2011. * Correspondence: Mr. Brendan Delehanty, University of Toronto at Scarborough, Biological Sciences, Toronto, ON, M1C 1A4, Canada, brendan.delehanty@utoronto.ca Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Brendan Delehanty Rudy Boonstra Google Brendan Delehanty Rudy Boonstra Google Scholar Brendan Delehanty Rudy Boonstra PubMed Brendan Delehanty Rudy Boonstra Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Sensitivity of a cirolanid isopod to human pressure

Cirolanid isopods are conspicuous members of the supralittoral and intertidal fringes of sandy beaches around the world, being dominant in terms of number or biomass. Excirolana braziliensis is one of the most abundant species on exposed sandy beaches, both urbanized and preserved, of Rio de Janeiro in southeast Brazil. Considering the negative effects of urbanization and human pressure on sandy beaches, this study aimed to analyze the population structure and reproductive aspects of E. braziliensis in different stretches of Barra da Tijuca beach (Rio de Janeiro, Brazil), which differ with respect to urbanization and occupation by bathers. Monthly samplings of E. braziliensis were conducted throughout 12 months within urbanized and preserved stretches, including measurements of beach parameters and human pressure. The anthropogenic effect seems to be a relevant factor in explaining the variability in the population structure of this species. Negative significant correlations were found between the species density and the number of visitors, who massively occupies the urbanized stretches. Similar life history strategies were observed for different populations of E. braziliensis. Although high fecundity rates were reported to all stretches, the probability of eggs/embryos survival under the adverse conditions provided by the Barra da Tijuca beach is not clearly known. According to the results of this study, it could be inferred that the human pressure over Barra da Tijuca beach affects the populations: (1) directly, through human trampling and/or natural habitat jeopardizing; or (2) indirectly, by the isolation of individuals in the preserved stretch, located between environments subjected to intense disturbance. In such case, the species strategy to thrive in a protected area of restricted size, within a highly urbanized and occupied area by bathers does not appear to be the best conservation measure for peracarid species, as in E. braziliensis. Nevertheless, E. braziliensis turned out to be a good monitoring species of impacts due to its high resistance to environmental stress, persisting in highly urbanized areas dominated by bathers.

Evaluating the power of surface attendance counts to detect long-term trends in populations of crevice-nesting auklets

Power analyses are essential when developing a long-term monitoring program for a target species whose observation is logistically challenging and expensive. These analyses can be complicated when the observations have a complex variance structure reflecting many factors. Crevice-nesting seabirds such as least and crested auklets Aethia pusilla and Aethia cristatella illustrate both this need and these challenges. They are ecosystem indicators for the Bering Sea, a system expected to undergo large changes. Unfortunately, they are difficult to monitor as colonies occur on remote, hard to access islands in the Aleutians and Bering Sea, and nests occur in crevices underground, preventing direct observation. Current monitoring consists of breeding-season counts of auklets standing on the surface of sample plots in the colony; logically, a substantial decline in nesting population guarantees an eventual substantial decline in surface attendants. Yet, it remains debatable whether these highly variable counts can be used to statistically detect biologically relevant declines in the attending population let alone the nesting population. Subsequently, existing monitoring programs vary widely in survey design, effort levels, and daily summary statistics. The power of different survey designs was assessed by simulating observations from a state model developed from 11 years of observations using mixed-effects models and zero-inflated Poisson-lognormal regression. The analyses illustrate the process required for any monitoring program whose observations are described inadequately by standard statistical models. State model development revealed survey design refinements that reduce sampling variation. For least auklets, current sampling efforts provided 90% power to detect annual declines of 11% ("Critically Endangered" using IUCN Red List criteria), 4.5% ("Endangered"), or 2.4% ("Vulnerable") in two, four, or six generations, respectively; crested auklets took a few years longer. Power was more sensitive to number of days than number of plots. Results appear robust across a range of bird densities, providing guidance for monitoring other colonies or crevice-nesting species with similar life history strategies. Research should now focus on illuminating the relationship between the attending and nesting populations. Given the frequency of complicated variance structures and zero counts in ecological data, the general statistical models used here should prove widely applicable.

A tool to identify pink salmon ( Oncorhynchus gorbuscha) × Chinook salmon ( O. tshawytscha) hybrids in the St. Marys River, Michigan–Ontario

The first putative hybrid between pink salmon ( Oncorhynchus gorbuscha) and Chinook salmon ( O. tshawytscha) in the Laurentian Great Lakes was reported in 1992. Since that time, many St. Marys River anglers have reported catching hybrid ‘pinook’ salmon, but their true identity was often undetermined. Although Great Lakes populations of pink and Chinook salmon exhibit similar life history strategies to their Pacific coast counterparts, temporal and spatial overlap of spawning activities in the St. Marys River has made hybridization between these species common. We examined meristic and morphometric data from pink, Chinook and hybrid salmon captured in the St. Marys River during spawning migrations from 1999 to 2002. In addition, we determined spawning migration timing, size structure, age-at-maturity, and sex ratios for pink salmon, Chinook salmon and their hybrids. Spawning migrations of hybrid salmon were composed primarily (93%) of male fish. Peak migration for hybrids (20–30 September) was intermediate to peak migrations for the parent species (pink salmon: 10–19 September, Chinook salmon: 01–10 October). Hybrid salmon were intermediate for most meristic and morphometric characters examined. Using meristic and morphometric data, multivariate models were built and tested to determine the utility of using these data to aid in the identification of hybrids and the parent species. The result was an easy-to-use identification tool that requires counts of only four characters (lateral line scales, gill rakers, branchiostegal rays, and mandibular teeth) to identify pink salmon, Chinook salmon, and their hybrids.

The geographic structure of morphological variation in eight species of fiddler crabs (Ocypodidae: genus Uca) from the eastern United States and Mexico

Species with larger geographic distributions are more likely to encounter a greater variety of environmental conditions and barriers to gene flow than geographically-restricted species. Thus, even closely-related species with similar life-history strategies might vary in degree and geographic structure of variation if they differ in geographic range size. In the present study, we investigated this using samples collected across the geographic ranges of eight species of fiddler crabs (Crustacea: Uca) from the Atlantic and Gulf coasts of North America. Morphological variation in the carapace was assessed using geometric morphometric analysis of 945 specimens. Although the eight Uca species exhibit different degrees of intraspecific variation, widespread species do not necessarily exhibit more intraspecific or geographic variation in carapace morphology. Instead, species with more intraspecific variation show stronger morphological divergence among populations. This morphological divergence is partly a result of allometric growth coupled with differences in maximum body size among populations. On average, 10% of total within-species variation is attributable to allometry. Possible drivers of the remaining morphological differences among populations include gene flow mediated by ocean currents and plastic responses to various environmental stimuli, with isolation-by-distance playing a less important role. The results obtained indicate that morphological divergence among populations can occur over shorter distances than expected based on dispersal potential.