摘要: Little Terns Sternula albifrons are estuarine birds extensively using increasingly urbanized coastal areas. Given the increased exposure of these ecosystems to anthropogenic activities, it is crucial to study the ecology of this species and interactions with human stressors to establish management measures. We collected regurgitates (n = 182) and blood samples (n = 48) to study Little Terns' diet, health condition and isotopic niche, and individually tracked breeding adults (n = 9, during 2021 and 2022) at 2 sandy beaches 21 km apart and located within Ria Formosa Natural Park, Algarve, Portugal. Although both areas are adjacent to foraging coastal marine areas and an estuarine lagoon system with saltpans, they differ in human disturbance. We also compared breeding success and adult health measures between these 2 colonies. The main prey for both populations were Sand Smelts Atherina spp. and Gobies Pomatoschistus spp., and no differences in delta 13C and delta 15N stable isotopic values between colonies were found. Tracking data revealed that individuals foraged in the surroundings of their breeding colonies. Entrance Channels and Ocean were the most frequently used habitats for foraging by individuals from the less disturbed colony. Adults from the more disturbed colony foraged mostly in Entrance Channels. Overall, all individuals tended to forage during daytime. There were no differences in health measures of individuals between colonies, though breeding success at the most disturbed colony was comparably lower. It is important to protect both breeding areas and adjacent foraging habitats for Little Terns, particularly given the expected increasing pressure from human activities on coastal areas worldwide.

摘要: Adaptation to different environments can lead to local adaptations that facilitate morphological divergence between closely related taxa, potentially leading to speciation. Quantifying habitat variation can thus provide valuable insights into evolutionary processes. Arboreal dwarf chameleons of the genus Bradypodion exhibit 3 distinct ecomorphological forms: forest, shrub, and little brown chameleons (LBCs). It is assumed these ecomorphs are the result of convergence among species that are in similar habitats regardless of ancestry, or in some cases, morphological conservatism and retention of an ancestral form that is adapted to a shared habitat type. If so, then the habitat of different ecomorphs would differ in vegetation structure. Our results show that vegetation structure in fynbos/grassy habitats is characterized by significantly narrower perches than shrubby habitats, but both have a largely vertical perch orientation. In contrast, forests have significantly fewer vertical perches than fynbos/grassy habitats with significantly thicker diameter perches. Accordingly, LBC and shrub species used more vertically oriented perches than forest species, suggesting that perch use corresponds with the most widely available perch angles. Although LBC chameleons used the smallest diameter perches, when corrected for body size, there was no difference in perch diameter among ecomorphs. These results suggest that the body size of LBC chameleons is constrained by the prevalence of small-diameter perches in their habitat. Species in habitats with wider perches attain larger body size. These findings support the notion that variation in perch structure is critical for phenotypic convergence that has resulted in the 3 Bradypodion ecomorphs.

摘要: Different habitat types exert particular challenges to ecological performance, ultimately having a strong influence on the evolution of morphology. Although it is well known that external morphology can evolve under the selective pressure of habitat structure, the evolutionary response of internal morphological traits remains vastly unexplored. Here, we test for morphological divergence between arenicolous and nonarenicolous species in a clade of tropidurid lizards, considering external morphological proportions and limb muscle dimensions. We found that arenicolous species seem to have evolved internal and external morphological adaptations that separate them from other habitat specialists. Moreover, comparative analyses suggested that the traits that differed the most between arenicolous and nonarenicolous lizards might have evolved divergently towards different optima. Additionally, the axis of higher morphological divergence between arenicolous and nonarenicolous species represented an important proportion of the morphological diversity within our sample, indicating that the hypothetical adaptive divergence of internal and external traits has contributed significantly to phenotypic diversity. Our results show that evolutionary associations between morphology and habitat use can be detected on both external body proportions and muscle morphology. Moreover, they highlight the emergent importance of internal anatomical traits in ecomorphological studies, especially when such traits are directly involved in determining functional performance.

摘要: Aposematism is an antipredator strategy in which conspicuous coloration acts as a warning of chemical defenses to potential predators. Evidence suggests that aposematism largely functions under positive frequency-dependent selection, which is thought to maintain uniformity of aposematic signals. Many studies of aposematic organisms have found evidence that color signals and defenses are positively correlated, indicating a quantitatively honest aposematic signal. Dendrobatid poison frogs represent a well-studied group of aposematic organisms that in addition to exhibiting a diversity of color signals also display unique defensive behaviors. Few studies have examined if both behavior and coloration act as quantitative honest signals of alkaloid defenses in poison frogs. We aimed to determine if coloration and behavior are quantitatively honest signals in the green and black poison frog (Dendrobates auratus) among 6 populations from Costa Rica. We (1) evaluated antipredator displays by using behavioral assays in the field, (2) assessed frog conspicuousness and pattern using digital images, and (3) quantified alkaloid profiles from frog skin secretions. We found that Pacific populations are less conspicuous in coloration, had greater quantities of alkaloids, and more frequently performed body-raising defensive behaviors when compared with Caribbean populations. Our results do not support the hypothesis that aposematic traits in D. auratus are quantitatively honest. Rather, our results suggest that phenotypic differences among populations may represent different phenotypic optima for advertising unprofitability to predators based on local environmental conditions, leading to the diversification of aposematic signals in this species.

摘要: Dietary specialists consume specific prey items, and they are often morphologically and behaviorally specialized to feed efficiently on those prey animals. Among specialist snakes, consumption of terrestrial arthropods is relatively rare. Because most terrestrial arthropods possess hardened sclerites and appendages, it is possible that snakes that feed on arthropods would show specialized prey-handling behavior. In this study, we describe prey-handling behavior of a snake feeding on terrestrial arthropods, which hitherto has not been well documented. We focused on Rhabdophis chiwen, which mainly feeds on earthworms, but also consumes lampyrine firefly larvae, sequestering cardiotonic steroids from them in its defensive organs, called nucho-dorsal glands. When feeding on earthworms, snakes showed size-dependent selection of swallowing direction, but this tendency was not observed when feeding on firefly larvae. Manipulation of firefly larvae did not seem to be efficient, probably because they possess sclerites and appendages such as legs that impede smooth handling. Although fireflies are an essential food for R. chiwen as a toxin source, our results showed that the snake is not adept at handling firefly larvae compared to earthworms, implying that dietary specialization does not necessarily accompany behavioral specialization. We discuss possible reasons for this inconsistency.

摘要: Understanding the genetic diversity-area relationship (GAR) is essential for comprehending how species adapt to environmental changes, as genetic diversity is an indicator of a species' adaptive potential. Variation in environmental adaptation capacity exists among species and animal taxa with different distribution areas, highlighting the importance of understanding the GAR. To obtain a more comprehensive understanding of the GAR in terrestrial vertebrates, we assessed both haplotype diversity-area and nucleotide diversity-area relationships using 25,453 cytochrome c oxidase subunit I (COI) sequences from 142 amphibian species, 574 bird species, and 342 mammal species. We found that both measures of genetic diversity increased with species range size across major animal groups. Nevertheless, the GAR did not differ among animal groups, while haplotype diversity performed better than nucleotide diversity in profiling the GAR, as indicated by higher R2 values. The difference in the modeling fit may stem from the distinct biological and mathematical significance of nucleotide diversity and haplotype diversity. These results suggest that the GAR follows similar rules among different animal taxa. Furthermore, haplotype diversity may serve as a more reliable indicator for assessing the potential effects of area size changes on animal populations and provide better guidance for conserving genetic diversity.

摘要: Variation in the vocal behavior of nonhuman vertebrates includes graded transitions and more dramatic changes. Wapiti males produce a reproductive bugle that has a fundamental frequency that surpasses 2,000 Hz with evidence of biphonation and other nonlinear phenomena. Here, we analyze the acoustic structure of captive wapiti vocalizations to compare the male bugle with 3 categories of distress vocalizations: neonate distress (capture) calls, calf isolation calls, and adult female isolation calls. These 4 high-arousal call categories serve a common general function in recruiting conspecifics but occur in different behavioral contexts (capture, isolation, reproduction). Our goal was to distinguish characteristics that vary in graded steps that may correspond to an animal's age or size from characteristics that are unique to the bugle. Characteristics of the high and loud fundamental (G0) varied in an age/size-graded manner with a decrease in minimum G0, an increase in the maximum and range of G0, with no evidence of sex differences. The nonlinear phenomena of deterministic chaos, biphonation, and frequency jumps were present in all 4 call categories and became more common from the distress vocalizations of neonates to calves to adult females to the male bugle. Two temporal characteristics sharply distinguished the bugle from the 3 categories of distress vocalizations: these included a prolonged call duration and a maximum G0 that occurred much later in the call for the bugle than for distress vocalizations. Our results suggest that distress vocalizations of different age groups and the reproductive bugle of wapiti share a high G0, with age/size-graded changes in G0 and nonlinear phenomena, but differ sharply in temporal characteristics.

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摘要: Although mollusks represent Earth's second most diverse invertebrate group, their natural history and ecology are still scarcely known. The compilation of non-traditional data, such as those from citizen science, represents an alternative to fill these gaps, particularly on striking land snail species such as Macrocyclis peruvianus. Based on long-term citizen science, we aimed to update and describe some basic ecological aspects, such as the distribution and protected area types used by M. peruvianus. We performed pairwise comparisons to test potential changes in occurrence and occupancy among administrative regions, forest types, and protected area types using chi-squared tests. The citizen scientists were also asked to provide the number of M. peruvianus individuals observed and the tree species that dominated their habitat. Thus, we tested if the number of land snails found by citizen scientists could be related to forest and protected area types using a generalized linear mixed model. We expanded the northern distributional limit, with Nothofagus, evergreen, and mixed forests far the most frequented by M. peruvianus. Parallelly, the occurrence of M. peruvianus in official protected areas (65.73%) was significantly higher than in privately owned areas. Moreover, we did not find associations between forest and protected area types with the number of M. peruvianus recorded. Although citizen science is a helpful method for obtaining novel information regarding the ecology of neglected species such as M. peruvianus, it also introduces spatial and occurrence biases explained by the access and attractiveness of the officially protected areas compared to privately owned patches of native forest.