摘要: The parent-offspring conflict in avian species encompasses resource allocation and a balance necessary for survival for both parties. Parental investment is modulated according to various factors, among which begging is important. Endogenous hormones, particularly corticosterone (CORT), play a role in modulating begging behavior. However, most studies on hormonal regulation of begging behavior induced elevated hormone levels in the offspring through feeding or injections, thus, limiting our knowledge of the evolution of the parent-offspring conflict under natural conditions. In this study, we aimed to identify the key signals that parents respond to during interactions with their nestlings in the wild, considering factors such as endogenous hormone CORT, nestling age, and brood size, which may affect nestling begging behavior. Begging performance was evaluated by measuring the begging frequency and score of the red-whiskered bulbul (Pycnonotus jocosus), along with assessing CORT levels in feathers. CORT levels were significantly correlated with both the begging frequency and score of nestlings, while variables such as body mass and tarsus length did not influence parental feeding frequency. Additionally, factors such as the number of nestlings (brood size), age, and begging frequency were predictors of parental feeding frequency. Our findings indicate that begging frequency, nestling age, and brood size are signals that help navigate the intricacies of the parent-offspring conflict and that parents may rely on these key signals from the range of begging cues exhibited by nestlings to adjust their feeding strategies.

摘要: Adaptation or acclimation of thermal requirements to environmental conditions can reduce thermoregulation costs and increase fitness, especially in ectotherms, which rely heavily on environmental temperatures for thermoregulation. Insight into how thermal niches have shaped thermal requirements across evolutionary history may help predict the survival of species during climate change. The lizard genus Sceloporus has a widespread distribution and inhabits an ample variety of habitats. We evaluated the effects of geographical gradients (i.e. elevation and latitude) and local environmental temperatures on thermal requirements (i.e. preferred body temperature, active body temperature in the field, and critical thermal limits) of Sceloporus species using published and field-collected data and performing phylogenetic comparative analyses. To contrast macro- and micro-evolutional patterns, we also performed intra-specific analyses when sufficient reports existed for a species. We found that preferred body temperature increased with elevation, whereas body temperature in the field decreased with elevation and increased with local environmental temperatures. Critical thermal limits were not related to the geographic gradient or environmental temperatures. The apparent lack of relation of thermal requirements to geographic gradient may increase vulnerability to extinction due to climate change. However, local and temporal variations in thermal landscape determine thermoregulation opportunities and may not be well represented by geographic gradient and mean environmental temperatures. Results showed that Sceloporus lizards are excellent thermoregulators, have wide thermal tolerance ranges, and the preferred temperature was labile. Our results suggest that Sceloporus lizards can adjust to different thermal landscapes, highlighting opportunities for continuous survival in changing thermal environments.

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: The brood-parasitic brown-headed cowbird (Molothrus ater) has one of the shortest incubation periods of any bird. Brown-headed cowbird eggs, and those of other avian brood parasites, tend to be more spherical due to their greater relative width. The traditional explanation for this egg shape is that it, combined with the thicker eggshells, resists host puncture-ejection. However, very few North American hosts of the brown-headed cowbird actually engage in puncture-ejection and therefore wider eggs may instead provide greater contact with a host's brood patch during incubation, especially in large host nests. We tested whether greater egg width increased mean temperature and reduced temperature variation in brown-headed cowbirds by inserting temperature probes into brown-headed cowbird and house sparrow (Passer domesticus) eggs and placing them into red-winged blackbird (Agelaius phoeniceus) nests. House sparrow eggs are similar in appearance and in length to cowbird eggs, but are not as wide. We found no significant relationship between brown-headed cowbird egg width and mean incubation temperature. However, brown-headed cowbird eggs experienced less temperature variation than house sparrow eggs, and within brown-headed cowbird eggs, more spherical eggs experienced less temperature variation when accounting for differences in width. These results suggest that brown-headed cowbirds may have short incubation periods in part because their eggs exhibit less temperature variation over the course of incubation. The brown-headed cowbird's egg shape may contribute to its accelerated embryonic development rate relative to host eggs of similar size, which explains its ability to hatch in a variety of host nests.

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.