Changes In Habitat Preference Research Articles

Distribution pattern and habitat use of the protandrous shrimp Pandalus latirostris in relation to environmental characteristics in Akkeshi waters on the pacific coast of eastern Hokkaido, Japan

A sampling of the protandric shrimp, Pandalus latirostris, was conducted at fixed sites from July 2015 to March 2020 in Akkeshi Bay and the connecting Lake Akkeshi on the Pacific coast of eastern Hokkaido. Based on the occurrence pattern of P. latirostris, most individuals begin mating as males at Age-1, followed by a sex change to females, spawn eggs as females at Age-2, and hatch their eggs in the spring of Age-3. Pre-hatching ovigerous females were mainly found in eelgrass beds near and in Lake Akkeshi, where the water temperature was relatively high. The females probably migrate there to hatch their eggs, making sure of the high survival and growth of the hatched larvae. Juveniles and small males were also abundant in near and in Lake Akkeshi, indicating that many larvae remained in the eelgrass beds where they hatched. These eelgrass beds play an important role in the maintenance of the shrimp population as a major egg-hatching site and nursery habitat in Akkeshi waters. With ontogenetic development, the occurrence rate of P. latirostris gradually increased on the offshore side of Akkeshi Bay, with its body size being larger. As P. latirostris grow, they will probably disperse to the offshore side of Akkeshi Bay. However, the density of P. latirostris in the eelgrass bed in the bay near the lake was extremely high, with its strong preference at all ontogenetic stages. This eelgrass bed would help maintain the shrimp population as a “key habitat” for the shrimp. The site-specific environmental characteristics of vegetation beds influence the distribution and abundance of individuals within a population of P. latirostris through their growth and the associated change in habitat preference. In this study, the importance of maintaining the diverse habitats of P. latirostris will be discussed as part of the shrimp stock management measures.

Shift in habitat selection during natal dispersal in a long‐lived raptor species

Animals select their habitat along environmental gradients, but the mechanisms that constrain the ecological requirements of an individual can differ between life stages. Dispersal is a key demographic process that determines gene flow and alters species distributions, yet few empirical studies have examined whether habitat selection in animals is changing during dispersal. In this study, we examined changes in habitat preferences during natal dispersal of red kites Milvus milvus, a European raptor species. By deploying solar‐powered GPS‐GSM transmitters on nestlings, we continuously tracked individuals up to six years (2015–2020), from fledging to settlement. We applied habitat selection functions (HSF) to the tracking data using hierarchical generalized additive models, a flexible method which combines individual‐ and population‐level inference, while allowing for the contrast of the prospecting and settlement phases. During the prospecting phase (n = 204 birds), individuals were less responsive to their environment than during the settlement phase, resulting in a predicted wide distribution in western Europe. During the settlement phase, individuals (n = 78 birds) selected a narrower range of environmental gradients, while avoiding areas of high elevation, steep topographic slopes, high human population density and highly heterogeneous landscapes. During this phase, individuals were also more philopatric, i.e. they were more inclined to choose an environment closer to their natal area, than during the prospecting phase. Suitable habitats predicted during settlement were much more spatially contrasted than during prospecting. Our study provides empirical evidence that habitat selection changes across natal dispersal phases in a long‐lived species, indicating that species conservation strategies should account for different environmental constraints before and after settlement. Furthermore, our findings underscore the importance of long‐term tracking data, with sufficient sample size, to study the link between habitat selection and natal dispersal.

Individual differentiation of habitat preferences indicate high flexibility in habitat use by European bison (Bison bonasus)

A typical challenge in studies on habitat selection is the creation of a global model at a population level. We focus upon an aspect frequently neglected in studies on habitat preferences - individual variability resulting from the ecological plasticity of a species. We studied European bison (wisent) Bison bonasus, inhabiting Białowieska Forest (north-eastern Poland), using data from GPS collars fitted on 11 individuals observed during 12–48 months, and demonstrated that habitat selection patterns in this population are highly variable. Even seasonal changes in habitat preference did not mitigate individual variability - during the same months, particular individuals of the same sex preferred certain habitats which were avoided by others. Therefore, even with fuzzy analysis, it was not possible to create clear rules for predicting habitat preferences for a given individual; only general patterns can be specified for seasonal avoidance of some habitats, rather than their positive selection. Hence, flexibility in habitat selection should be considered in planning the reintroduction of this species into new sites because it could considerably enhance the assumed available spectrum of suitable habitats. Moreover, since the natural dispersion of animals is not limited to forest complexes, new challenges for conservation as well as new limiting factors resulting from social conflicts could appear which should be taken into account in conservation planning, especially in agricultural areas.

Influence of prey availability on habitat selection during the non-breeding period in a resident bird of prey

BackgroundFor resident birds of prey in the temperate zone, the cold non-breeding period can have strong impacts on survival and reproduction with implications for population dynamics. Therefore, the non-breeding period should receive the same attention as other parts of the annual life cycle. Birds of prey in intensively managed agricultural areas are repeatedly confronted with unpredictable, rapid changes in their habitat due to agricultural practices such as mowing, harvesting, and ploughing. Such a dynamic landscape likely affects prey distribution and availability and may even result in changes in habitat selection of the predator throughout the annual cycle.MethodsIn the present study, we (1) quantified barn owl prey availability in different habitats across the annual cycle, (2) quantified the size and location of barn owl breeding and non-breeding home ranges using GPS-data, (3) assessed habitat selection in relation to prey availability during the non-breeding period, and (4) discussed differences in habitat selection during the non-breeding period to habitat selection during the breeding period.ResultsThe patchier prey distribution during the non-breeding period compared to the breeding period led to habitat selection towards grassland during the non-breeding period. The size of barn owl home ranges during breeding and non-breeding were similar, but there was a small shift in home range location which was more pronounced in females than males. The changes in prey availability led to a mainly grassland-oriented habitat selection during the non-breeding period. Further, our results showed the importance of biodiversity promotion areas and undisturbed field margins within the intensively managed agricultural landscape.ConclusionsWe showed that different prey availability in habitat categories can lead to changes in habitat preference between the breeding and the non-breeding period. Given these results we show how important it is to maintain and enhance structural diversity in intensive agricultural landscapes, to effectively protect birds of prey specialised on small mammals.

Changes in the Habitat Preference of Crested Ibis (Nipponia nippon) during a Period of Rapid Population Increase.

Simple SummaryIn 1981, the crested ibis (Nipponia nippon) was a critically endangered bird with only two pairs left in the world. Now, numbers have increased, and it has been reintroduced to many places in China, Japan, and Korea. In the breeding season, the crested ibis has high food needs (fish, freshwater invertebrate, etc.) to feed nestlings, and it prefers areas with rice paddies and waterbodies near to trees for nesting. We compared nest site preference from 1981 to 2019, and found that nest sites moved closer to houses of local farmers. In the 1980s, crested ibises only lived in remote mountain areas, where the farmers were too poor to afford pesticide and fertilizer, and consequently rice paddies contained substantial fish populations. In the meantime, the massive use of pesticides in more populated areas had caused the collapse of fish populations. A pesticide ban was enforced from 1981 on, when the crested ibis was rediscovered, and the freshwater biodiversity gradually recovered. The crested ibis returned to lower and more populated areas containing their ancestral habitats with large areas of wetlands.The number of breeding pairs of crested ibis (Nipponia nippon) in Hanzhong, China has recovered remarkably from 2 to 511 from 1981 to 2019. Although the crested ibis has been closely monitored, the habitat preference of the bird has not been well studied despite the extensive increase in abundance. We used nest site data from the past 39 years and 30 environmental variables to develop species distribution models for each year. We applied random forest to select important environmental variables, and used logistic regressions to quantify the changes in habitat preferences in 39 years, taking into account the effects of interaction and quadratic terms. We found that six variables had strong impacts on nest site selection. The interaction term of rice paddies and waterbodies, and the quadratic term of precipitation of the wettest quarter of the year were the most important correlates of nest presence. Human impact at nest sites changed from low to high as birds increased their use of ancestral habitats with abundant rice paddies. We concluded that during the population recovery, the crested ibises retained their dependence on wetlands, yet moved from remote areas to populated rural regions where food resources had recovered due to the ban of pesticide use.

Quantifying habitat preference of bottom trawling gear

Abstract Continental shelves around the world are subject to intensive bottom trawling. Demersal fish assemblages inhabiting these shelves account for one-fourth of landed wild marine species. Increasing spatial claims for nature protection and wind farm energy suppresses, however, the area available to fisheries. In this marine spatial planning discussion, it is essential to understand what defines suitable fishing grounds for bottom trawlers. We developed a statistical methodology to study the habitat preference of a fishery, accounting for spatial correlation naturally present in fisheries data using high-resolution location data of fishing vessels and environmental variables. We focused on two types of beam trawls to target sole using mechanical or electrical stimulation. Although results indicated only subtle differences in habitat preference between the two gear types, a clear difference in spatial distribution of the two gears was predicted. We argue that this change is driven by both changes in habitat preference as well as a change in target species distribution. We discuss modelling of fisheries’ habitat preference in light of marine spatial planning and as support in benthic impact assessments.

Behavioral Changes in Tadpoles of the Antillean White Lipped Frog (Leptodactylus albilabris) in the Presence of a Predator: Habitat Use Preference and Activity Levels

This study is based on the behavioral responses of Leptodactylus albilabris tadpoles, a widely abundant frog native to Puerto Rico. We evaluated changes in habitat preference and activity levels in the presence of a predator (fish). Tadpoles were collected and allocated to one of three treatments: no fish predator, one fish (Astronotus ocellatus), and two fish. Results showed a significant decrease in activity levels of tadpoles and change in microhabitat use in the presence of a predator. However, there was no significant difference in tadpole activity when the second predator was added. The preferred habitat in the presence of a predator was leaf litter, even though L. albilabris tadpoles are benthic and usually favor hiding in the sediment. The larval stage of the anuran life cycle is the most vulnerable, and these changes in behavior increase the probability of escaping predators to reach metamorphosis and finally reproduce.

Deep water fish ontogenic changes in habitat preferences in several NE Atlantic ecosystems

Deep water fish ontogenic changes in habitat preferences in several NE Atlantic ecosystems

Phylogenetic Analysis Reveals that the ‘Radial Centric’ Diatom Orthoseira Thwaites (Orthoseiraceae, Bacillariophyta) is a Member of a ‘Multipolar’ Diatom Lineage

The diatom genus Orthoseira Thwaites (Bacillariophyta) is a ubiquitous taxon in aerial diatom assemblages, with species found globally. Cylindrical cell shape and radial symmetry of this genus has led to its historical placement in the Coscinodiscophyceae ('radial centric' diatoms), but its systematic relationships have remained uncertain. We present a five-gene phylogeny, based on nuclear (nSSU rDNA) and chloroplast (rbcL, psbC, psbA, and psaB) genes to determine the phylogenetic placement of Orthoseira among the diatoms. The concatenated multi-gene phylogenies and nSSU-only gene tree demonstrate that Orthoseira is deeply embedded within a clade of the Mediophyceae ('multipolar centric' diatoms). Throughout all phylogenetic analyses, Orthoseira was shown to be sister to the genera Terpsinoë and Hydrosera. Through comparison of topologies reflecting competing hypotheses about the placement of Orthoseira, it was determined that the hypothesis that Orthoseira, represented here by O. dendroteres and O. roeseana, is a member of the Melosirales should be rejected. Therefore, lack of morphological similarity between Hydrosera, Orthoseira, and Terpsinoë is hypothesized to be the result of changes in habitat preferences that lead to an ancient divergence event between the Orthoseirales and the Hydrosera, Terpsinoë clade.

Distribution, demography, and behavior of North Atlantic right whales (Eubalaena glacialis) in Cape Cod Bay, Massachusetts, 1998–2013

AbstractThe occurrence of North Atlantic right whales (Eubalaena glacialis) in Cape Cod Bay was documented during aerial surveys between 1998 and 2013. The seasonal occurrence remained relatively unchanged during the study, spanning the January through mid‐May timeframe. The number of individual whales visiting the Bay was positively correlated with the increasing Best Cataloged Estimate (BCE), the number of photographed whales alive, with a maximum in 2011 of 56.9% (n = 277) of BCE. However, the rate of increase in number of individuals during the study was significantly greater than that of the BCE (difference in slope: 12.72; P < 0.01) suggesting that increased visitation to the Bay was due in part to a change in habitat preference. Although the demographic composition of whales observed during the study differed little from that of the cataloged whales, the proportion of calves born in the North Atlantic that were documented in the Bay increased significantly (P < 0.01). Models of random visitation demonstrated an individual preference for or rejection of the Bay by the right whales of the North Atlantic population.

Adult avoidance behavior leads to ontogenetic shifts in habitat use of an intertidal fish

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 585:143-154 (2017) - DOI: https://doi.org/10.3354/meps12386 Adult avoidance behavior leads to ontogenetic shifts in habitat use of an intertidal fish Amy F. Ritter1,2,* 1Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, 1156 High Street, Santa Cruz, California 95064, USA 2Station d’Ecologie Expérimentale du CNRS USR2935, 09200 Moulis, France *Corresponding author: ritter@biology.ucsc.edu ABSTRACT: Spatial distributions of organisms result from a complex interplay of processes, including habitat selection as well as species interactions, and it remains a continual challenge to disentangle the relative importance of such effects. I investigated how habitat variation and conspecific interactions influence the abundance and distribution of different life history stages of the intertidal fish Oligocottus snyderi. I first examined the role of priority recruitment effects and found that prior recruitment had no effect on subsequent O. snyderi recruitment. I then examined how habitat variation influences adult and recruit abundances by manipulating surfgrass Phyllospadix spp. cover in tide pools, a habitat attribute that positively covaries with both O. snyderi life history stages. Surprisingly, whereas O. snyderi adults showed the expected negative response to surfgrass removal, the recruit response was positive. Additional experiments investigated whether these contrasting results were due to an ontogenetic change in habitat preference or to negative interactions between adults and recruits. Direct manipulation of adult abundance in the field determined that O. snyderi recruit abundance increases when adult abundance decreases. Laboratory studies indicated that although O. snyderi recruits have little to no preference for surfgrass cover, they do exhibit a strong negative reaction to conspecific adults and adjust their distributions accordingly. This combination of field and laboratory studies suggests that the ontogenetic habitat shift of O. snyderi is actually a result of negative interactions between size classes, such that recruits settle into sub-optimal tide pools in order to avoid interacting with adults. KEY WORDS: Habitat variation · Conspecific interactions · Intraspecific competition · Aggregation · Recruitment · Oligocottus snyderi Full text in pdf format PreviousNextCite this article as: Ritter AF (2017) Adult avoidance behavior leads to ontogenetic shifts in habitat use of an intertidal fish. Mar Ecol Prog Ser 585:143-154. https://doi.org/10.3354/meps12386 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 585. Online publication date: December 22, 2017 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2017 Inter-Research.

Preference by juvenile Chinese sucker Myxocyprinus asiaticus, for substrate colour in zero versus slow velocity regimes suggest a change in habitat preference of wild juveniles after damming the Yangtze river

AbstractHabitat preference of benthic riverine juvenile Chinese sucker, Myxocyprinus asiaticus, a protected species in China, is poorly understood. This situation makes it difficult to evaluate the potential impacts on juveniles after river alteration. To better understand the impact of damming, we studied preference of cultured juvenile Chinese sucker (7.90–8.55 cm, standard length) for dark versus light substrate colours in 2 velocity regimes: zero velocity (like on a reservoir bottom) and in a slow water current of 0.15–0.19 cm/s (like on the bottom of a slow flowing stream). In the slow current regime, juveniles chose black substrate during the day and night. This likely represents the natural substrate preference by wild suckers in a river. However, in the zero velocity regime, juveniles chose a black substrate during the day, but switched preference to a white substrate at night. The results suggest wild juveniles in the natural Yangtze River have evolved a preference for a black substrate during the day and night. However, after the river was impounded by the Three Gorges Dam and bottom velocity changed to a static regime, juveniles in the reservoir changed substrate colour preference and now prefer a light‐coloured substrate colour at night. Thus, damming likely caused a major behavioural change by juveniles. The adaptive significance and effect on fitness of this change in habitat preference is not known but should be investigated as wild Chinese sucker continue to decline in abundance.

Changes in habitat preference of tuna species and implication for regional fisheries management: southern bluefin tuna fishing in the Indian Ocean

ABSTRACTChanges in the ocean’s physical environment and its impact on ecosystems are well recorded in the literature and are likely to impact on the range and distribution of tuna species. This paper examines the impacts of these factors on the southern bluefin tuna (SBT) (Thunnus maccoyii), a species of low population abundance that is the focus of a high-value fishery. Oceanic warming has been projected to facilitate the expansion of such tropical tunas whilst reducing the northern distribution of temperate tunas such as the SBT. The study analysed the distribution of SBT using historical fisheries data collected by the Commission for the Conservation of SBT and the Indian Ocean Tuna Commission with the latitudes of fishing events and catches used as a proxy for SBT presence. Whilst these data do not provide conclusive evidence of a southerly shift in habitat preference, they do show increasing overlap between the SBT and with yellowfin tuna (Thunnus albacares). The paper concludes that while shifts in fishing effort in the Indian Ocean have a number of potential drivers, including changes in fish habitat, they highlight potential challenges to current regional management arrangements.

Paleobiology of the Latest Tithonian (Late Jurassic) Ammonite Salinites grossicostatum Inferred from Internal and External Shell Parameters.

Based on material from the uppermost Tithonian La Caja Formation at Puerto Piñones, northeastern Mexico, the complete ontogenetic development (protoconch to adult) of the ammonite Salinites grossicostatum is outlined by a detailed morphometrical shell analysis. The embryonic stage, consisting of a small ellipsoid protoconch and ammonitella, ends at about 0.6 mm. Four major morphological changes are differentiated throughout ontogeny based on internal features such as reduced septal spacing and siphuncle position. Sexual dimorphism is reflected by shell size, siphuncular diameter, differences in the morphology of the apophysis, and by two distinct general trends in septal spacing. In addition, macroconchs are characterized by septal crowding at different stages, followed by the return to normal septum distances. Our analysis indicates a change in the mode of life after the neanic stage. A change in habitat preference is inferred for adult individuals. While microconchs persisted at Puerto Piñones, large mature macroconchs temporarily migrated to other areas, possibly for egg deposition. Salinites grossicostatum is endemic to the ancient Gulf of Mexico and is there restricted to outer continental shelf environments.

Influence of temperature and congener presence on habitat preference and fish predation in blue (Paralithodes platypus Brandt, 1850) and red (P. camtschaticus Tilesius, 1815) king crabs (Anomura: Lithodidae)

Rebuilding fisheries is a difficult process and many stocks that are declared overfished fail to recover even in the absence of fishing pressure. The Pribilof Islands stock of the blue king crab ( Paralithodes platypus Brandt, 1850) in Alaska, USA is one of these recovery failures. To explore how environmental and ecological factors might interact to suppress this stock, we conducted a suite of laboratory experiments to assess the effects of temperature changes and the presence of red king crab ( Paralithodes camtschaticus Tilesius, 1815) on blue king crab habitat preference and fish predation survival. Age-0 blue king crabs exhibited plasticity in habitat preference mediated by changes in water temperature, as well as the presence and density of juvenile red king crabs. While blue king crabs are often associated with shell-hash habitat, increases in water temperature, as well as the presence of red king crab at high densities, caused blue king crab juveniles to shift into habitats with an algal mimic present, a habitat type shown to reduce the predation efficacy of red king crabs. In contrast, red king crabs exhibited fewer changes in habitat preference with changes in water temperature and the presence of a congener. Blue king crabs are therefore behaviorally plastic, switching from strategies of predator avoidance when predator encounter rates are likely low, to predator deterrence strategies when encounter rates are higher. Fish predation trials further support the idea that blue king crabs are more focused on predator avoidance than are red king crabs. In fish predation trials run separately for the two crab species, blue king crabs had higher survival (60%) than red king crabs (33%) when exposed to fish predators. Our results indicate that age-0 blue king crabs can be less vulnerable to fish predation than red king crabs, but future research should assess how fish predation rates change when presented with higher densities of red and blue king crab in mixed assemblages as the observed habitat shifts could affect predation survival.

Evidence for the buffer effect operating in multiple species at a national scale.

A long-standing aim of ecologists is to understand the processes involved in regulating populations. One such mechanism is the buffer effect, where lower quality habitats are increasingly used as a species reaches higher population densities, with a resultant average reduction in fecundity and survival limiting population growth. Although the buffer effect has been demonstrated in populations of a number of species, a test of its importance in influencing population growth rates of multiple species across large spatial scales is lacking. Here, we use habitat-specific population trends for 85 bird species from long-term national monitoring data (the UK Breeding Bird Survey) to examine its generality. We find that both patterns of population change and changes in habitat preference are consistent with the predictions of the buffer effect, providing support for its widespread operation.

Aspects of the biology and life history of largespot pompano, Trachinotus botla, in South Africa

Trachinotus botla is an important recreational surf zone-dependent fish species distributed in the Indo-west Pacific from South Africa to Australia. In South Africa it is restricted to the northern KwaZulu-Natal coast. Biological investigations revealed that it is a fast growing species that attains a maximum age of ~7 years. Males and females sexually matured in their third year. It has a protracted summer spawning season with evidence of serial spawning behaviour. T. botla is an opportunistic predator with a generalist diet, with fish feeding on a wide variety of prey items particularly those that are temporally ‘superabundant’. Small fish fed predominantly on copepods and terrestrial insects, whereas larger fish consumed bivalves and crabs. Teleosts, primarily engraulids, were important components to the diet of fish of all sizes. An ontogenetic dietary shift was observed just after sexual maturity (~300-mm fork length) that is possibly linked to a change in habitat preference with larger fish foraging on deeper reefs.

Stimulus-specific development of learning ability during habitat shift in pre to post-recruitment stage jack mackerel

Marine fishes often experience major habitat shifts during their life history, and previous studies have shown that the learning capability of fish change ontogenetically and in accordance with such habitat shifts. However, because all of these studies used a single type of conditioned stimuli (CS), they failed to detect qualitative changes in learning capability. Here we tested the hypothesis that preparedness for learning changes ontogenetically in jack mackerel Trachurus japonicus, which undergo a drastic change in habitat preference during their life history as they move from offshore pelagic waters to coastal and demersal rocky reefs. Groups of juveniles measuring 40 mm standard length (SL) (pelagic stage) and 60 mm SL (demersal stage) were conditioned to food rewards in response to three different CS; the presence of a surface structure, mid-water structure, and aeration. The results showed that small juveniles tended to become conditioned to the surface stimulus faster than they did to the mid-water stimulus. Conversely, large juveniles responded to the mid-water stimulus significantly more quickly than they did to the surface stimulus. These results suggest that stimulus-specific learning capability in T. japonicus changes ontogenetically, facilitating adaptation to their life-history strategy.

Molecular inference of a Late Pleistocene diversification shift inNigellas. lat. (Ranunculaceae) resulting from increased speciation in the Aegean archipelago

AbstractAim To infer the temporal course and geographical mode of speciation in Mediterranean/Southwest AsianNigellas. lat.Location Mediterranean Basin, Aegean archipelago.Methods Phylogenies forNigellaL. andGaridellaL. (= Nigellas. lat.) were obtained from maximum‐likelihood analyses of internal transcribed spacer (ITS) sequences. Diversification through time was analysed by log lineages‐through‐time (LTT) plots and survival analyses. Relative node age estimates were regressed against the degree of sympatry between sister clades to infer the predominant mode of geographical speciation inNigellas. lat.Results The Late Pleistocene radiation of theNigella arvensiscomplex in the Aegean region caused a significant departure from a stochastic speciation/extinction process of diversification during the evolution ofNigellas. lat., a lineage of (at least) Late Miocene origin. Speciation withinNigellas. lat. predominantly took place in allopatry.Main conclusions No significant effect on diversification rate was found regarding the establishment of a Mediterranean‐type climate, or the onset of the Quaternary climatic oscillations. Rather, the accelerated rate of speciation in theN. arvensiscomplex is plausibly related toincreasedopportunities for allopatric speciation afforded by the (palaeo)geographical complexity of the Aegean archipelago combined with Late Pleistocene changes in climate and sea level. The evolution of self‐pollination and associated changes in habitat preference and flowering time further augmented speciation and niche differentiation within the complex, but these changes did not act as the primary promoters of the radiation process.

A Phylogenetic Analysis of Sexual Size Dimorphism in Turtles

Sexual size dimorphism (SSD) is widespread in a variety of vertebrate taxa, and its presence has been associated with a range of evolutionary and ecological factors. Turtles, as a lineage, have been shown to include species that exhibit both forms of SSD—male-biased (male larger) and female-biased (female larger)—as well as species that do not exhibit SSD (male size ≅ female size). Previous work has suggested that factors affecting the direction and magnitude of SSD in turtles may include habitat preference and fecundity; these correlations, however, have not been tested in a phylogenetic context. To provide a framework for evaluating potential correlates with the magnitude and direction of SSD in turtles, we examined the phylogenetic distribution of SSD in this clade. Published sources were surveyed for data on the direction and magnitude of SSD, carapace length, clutch size, egg size, and preferred habitat (terrestrial vs. nonterrestrial). Phylogenies were compiled from multiple published sources to develop a phylogeny for all taxa (n = 82) for which SSD data were assembled. The phylogenetic distribution of SSD was then evaluated using parsimony-based methods. These analyses indicated that the ancestral condition for extant turtles was female-biased SSD. Phylogenetic analyses conducted on subsets of the data (concentrated-changes tests, independent contrasts) indicated that changes in SSD state were not correlated with changes in habitat preference. Both male and female carapace length were found to be correlated with traits related to fecundity (egg size, clutch size), but the degree of dimorphism was not found to be correlated with these traits. A significant negative correlation between egg size and clutch size was also evident in turtles, as predicted by life-history theory.