Evolutionary Ecology最新文献

Tufted Titmice (Baeolophus bicolor) (TUTI) and Black-crested Titmice (Baeolophus atricristatus) (BCTI) are sister species that hybridize within a narrow east–west contact zone that extends from central Texas into southwest Oklahoma. The zone corresponds with an ecotone that transitions from closed-canopy deciduous forests in the east, occupied by TUTI, to arid and open woodlands in the west occupied by BCTI. Furthermore, the ecotone encompasses areas impacted by urban and suburban development. We tested whether landscape-level landcover characteristics found within the TUTI × BCTI hybrid zone influence the abundances of the two parent species and their hybrids. We predicted that the parent species would differ in their habitat associations and hybrids would associate with habitats intermediate between that of TUTI and BCTI and with human disturbed habitats. In ArcGIS Pro, we used a grid-based sampling design to extract estimates of six land cover variables (derived from National Landcover Database data) and TUTI, BCTI, and hybrid abundances (derived from eBird data). Partial redundancy analysis (RDA) was used to examine the habitat associations of the three titmice types. The results revealed that TUTI associated most strongly with the percentage of mixed forest cover, and BCTI with the percentage of evergreen forest cover and impervious surface cover. No single landcover variable could be identified as a definitive association for hybrids, however, hybrid individuals do appear to be more abundant in a habitat type that is intermediate between that of the two parent species. Future studies should incorporate genotypic data from titmice in the hybrid zone and analyze habitat associations at finer spatial scales to gain a more conclusive understanding of the patterns detected in this broad scale study.

Fernandez-Duque et al. (Evol Ecol 37:859-869, 2023) reported instances where fledglings, able to move freely, were found in the nests of others of the same species containing chicks that were too young to fly. Interestingly, the foster parents fed these intruder fledglings. The researchers identified this as a novel behavior and termed it “Nest Integration.” However, this behavior had been documented previously as “nest switching” in both ornithological and behavioral literature. By integrating the findings of Fernandez-Duque et al. with the literature on nest switching, the evolution of nest switching highlighted by them, and the conditions that might promote it, could be better understood.

The mechanical strengthening of leaves protects seedlings from herbivore damage, particularly in shade-tolerant evergreens. Interspecific studies have shown that leaf mass per area (LMA) and leaf toughness (force-to-punch) can play this role. Here we compared the influence of LMA and leaf toughness on herbivory and plant performance in a temperate rainforest. In seedlings of 14 evergreen species, we addressed the across-species relationship between LMA and force-to-punch, and compared the strength of their associations with herbivory and with species’ light requirements. Moreover, in four understory species we performed a multivariate analysis within-species, analogue to phenotypic selection analysis, evaluating the correlation between seedling performance, estimated as chlorophyll fluorescence (F_v/F_m), and force-to-punch, LMA, lamina density and lamina thickness. LMA and force-to-punch were positively associated across species. Herbivory was negatively correlated with both force-to-punch and LMA, but a stepwise multiple regression showed that force-to-punch was a better predictor of herbivory. Neither leaf lamina density nor thickness were associated with herbivore damage. Those species that were more shade-tolerant had leaves with higher force-to-punch and higher LMA, and less slender seedlings. In the within-species analyses in four shade-tolerant species, seedling performance was generally positively associated with force-to-punch, but not with LMA, lamina thickness, or lamina density. Both interspecific and within-species analyses showed that force-to-punch is more strongly related to herbivore damage and plant performance than LMA. This consistency between interspecific patterns of trait covariation and within-species trait-performance associations suggests that natural selection could have shaped the relationships between mechanical traits and ecological roles observed across species.

Aposematic organisms rely on their bright conspicuous coloration to communicate to potential predators that they are toxic and unpalatable. These aposematic phenotypes are strongly tied to survival and therefore make excellent opportunities to investigate the genetic underpinning of coloration. The genus Ranitomeya includes phenotypically diverse members of Neotropical aposematic poison frogs native to South America. Significant progress has been made in elucidating the molecular mechanisms responsible for aposematic coloration in poison frogs, which have paved the way for future studies to test hypotheses of the evolution of coloration across aposematic vertebrates. However, very little is known about whether these color related genes are under positive selection. We assembled transcriptomes from publicly available data reads sets for 9 different color morphs of poison frogs in the Ranitomeya genus that display bright conspicuous coloration (four morphs of R. imitator, two morphs of R. variabilis, two morphs of R. fantastica, one morph of R. summersi) to identify protein-coding genes responsible for color production that are under positive selection. Our results show that there are multiple genes under strong positive selection that are predicted to play roles in melanin synthesis (dct, tyrp1, irf4), iridophore development (fhl1), keratin metabolism (ovol1), pteridine synthesis (prps1, xdh), and carotenoid metabolism (adh1b, aldh2). The identification of positive selection affecting candidate color-pattern genes is consistent with the possibility that these genes mediate (in part) the molecular evolution of coloration. This may be attributed to aposematic phenotypes being directly tied to survival and reproduction in poison frogs.

Sexual size dimorphism (SSD) is a widespread phenomenon in the animal world resulting from differential selection on the sexes. The northern pike (Esox lucius) is a freshwater apex predatory fish species that exhibits female-biased SSD, but the degree to which SSD varies among populations and what variables might dictate variation in SSD in this species remain poorly understood. We sought to quantify the degree of variation in SSD among northern pike populations across a large portion of their North American range, as well as evaluate associations between the magnitude of SSD in northern pike populations with environmental variables and life history traits of populations. We quantified SSD in 102 populations of northern pike across the province of Ontario, Canada, using a standardized gillnetting database, and investigated the degree to which both environmental variables (cisco [Coregonus artedi] abundance as catch-per-unit-effort, lake surface area, and latitude) and northern pike life-history traits (early growth and mortality rates) explained variation in female-biased SSD using linear models. Female-biased SSD in mean weight of northern pike increased with increasing cisco abundance, and the difference in female and male mean age increased with increasing latitude. Furthermore, SSD was greater in populations with lower female mortality and early growth rates. These results indicate that slow-growing, long-lived populations of northern pike should exhibit greater female-biased SSD, and that these conditions may be facilitated by the availability of large, energy-dense prey and cooler temperatures at northern latitudes.

Animal and plant colouration presents a striking dimension of phenotypic variation, the study of which has driven general advances in ecology, evolution, and animal behaviour. Quantitative Colour Pattern Analysis (QCPA) is a dynamic framework for analysing colour patterns through the eyes of non-human observers. However, its extensive array of user-defined image processing and analysis tools means image analysis is often time-consuming. This hinders the full use of analytical power provided by QCPA and its application to large datasets. Here, we offer a robust and comprehensive batch script, allowing users to automate many QCPA workflows. We also provide a complimentary set of useful R scripts for downstream data extraction and analysis. The presented batch processing extension will empower users to further utilise the analytical power of QCPA and facilitate the development of customised semi-automated workflows. Such quantitatively scaled workflows are crucial for exploring colour pattern spaces and developing ever-richer frameworks for analysing organismal colouration accounting for visual perception in animals other than humans. These advances will, in turn, facilitate testing hypotheses on the function and evolution of vision and signals at quantitative and qualitative scales, which are otherwise computationally unfeasible.

Abstract

Despite the current disjoint distribution of Amazonian and Atlantic forests, evidence suggests past historical connections. Here we investigated the historical connections between three didelphid mammal species from Amazonian and Atlantic forests (Caluromys philander, Marmosa demerarae, and M. murina) using comparative phylogeography and paleodistribution models. We generated ecological niche models from the present until the Pliocene to evaluate changes in distributions over time, focusing on the previously suggested connection routes. We inferred divergence times between populations of each species using the mitochondrial Cytochrome b, estimated the phylogeographic relationships with haplotype networks, and calculated the genetic distances. All species exhibited populations that were separated between the Amazonian and Atlantic forests around 1–2 million years ago, while some populations showed more recent divergences. Paleodistributions were more extensive for periods predating the estimated times of divergence for all species, becoming narrower after this period. We suggest that the climatic oscillations during the onset of the Pleistocene largely influenced the phylogenetic structuring of these forest-dwelling species. This led to the separation of populations currently restricted to Amazonian or Atlantic forests. Our findings also point to repeated connections over time, with both North- and South-Eastern routes compatible with ancient connections. This represents the first simultaneous evaluation of past connections between Amazonian and Atlantic forests combining phylogeographic inferences with paleodistribution models for didelphid marsupials. We suggested the relation of the responses to past climate change, such as increases in the paleodistribution, and species resilience.

Some of the most impactful invasive plants are hybrids that exhibit heterosis and outperform their parent species. Heterosis can result from multiple genetic processes, and may also be more likely when parental populations are inbred. However, although outcrossing between relatives and self-fertilization both occur in many widespread plants, no study to our knowledge has investigated whether inbreeding in parental populations could help to explain heterosis in hybrid plants that have displaced their parent species. In the wetlands of southeastern Canada there is a widespread Typha (cattail) hybrid zone in which native T. latifolia (broad-leafed cattail) interbreeds with introduced T. angustifolia (narrow-leafed cattail) to produce the invasive hybrid T. × glauca. Typha reproduce through self-fertilization, outcrossing, and clonal propagation. Heterosis has been identified in T. × glauca by comparing proxy fitness measures between hybrids and parent species, but these studies did not consider the potential importance of inbreeding in parental populations. Because F1 hybrids have higher heterozygosity than their parent species, the self-fertilized offspring of hybrids should have higher heterozygosity than the self-fertilized offspring of parent species; the latter should therefore be more inbred, and potentially more susceptible to inbreeding depression (ID). We tested the hypothesis that self-fertilization leads to greater ID in the offspring of T. latifolia and T. angustifolia compared to the offspring of F1 T. × glauca. We conducted common-garden and wetland experiments using seeds from hand-pollinated plants sourced from natural populations, and quantified several fitness-related metrics in the offspring of self-fertilized versus outcrossed parent species and hybrids. Our experiments provided no evidence that inbreeding leads to ID in self-fertilized T. angustifolia, T. latifolia or T. × glauca in either a common garden or a natural wetland, and thus show that heterosis in a widespread invasive hybrid does not rely on comparisons with inbred parents.

Iris patterns in the animal kingdom are incredibly variable, with anurans having some of the most diverse and intricate patterns. Although the shape and colouration of anuran eyes seem to be correlated with ecological factors, the evolution of iris patterns remains unexplored. We used a large-scale phylogenetic comparison with 960 anuran species to examine the evolutionary and ecological correlates of iris patterns. We classified iris patterns into four broad categories: Reticulated, Plain, Dotted, and Lined, and examined whether iris pattern was correlated with diel activity (diurnal, nocturnal, and cathemeral activity) and habit (aquatic, arboreal, terrestrial, and fossorial) or both. Our analysis suggests that reticulated irises are the most common pattern in anurans and are the most likely ancestral character. The evolution of iris patterns across the anuran phylogeny best matched Brownian expectations, with many transitions between the four pattern types. Iris patterns, however, were mostly uncorrelated with diel activity or habit. The only exception was an association between plain irises and diel activity. Specifically, anurans with plain irises were more likely to be diurnal and less likely to be nocturnal; and the evolution of plain irises seemed to have preceded the evolution of diel activity. Overall, iris patterns across anurans are mostly unrelated to ecological factors, suggesting that this trait may be important for other functions, such as inter- or intra-specific interactions, or that the incredible diversity has evolved through neutral processes. Our findings open avenues for further research, especially to understand the potential adaptive value of the striking ornamentation in iris patterns across taxonomic groups.

Aposematism (considered here as an association between conspicuous colour patterns and the presence of a harmful secondary defence) has long been recognized as an anti-predator strategy, with salient traits serving as a warning signal to ward off would-be predators. Here we review evidence for a potentially widespread yet under-explored third component of this defensive syndrome, namely capture tolerance (the ability of the signaller to survive being captured and handled by would-be predators). We begin by collating the (largely anecdotal) available evidence that aposematic species do indeed have more robust bodies than cryptic species which lack harmful secondary defences, and that they are better able to survive being captured. We then present a series of explanations as to why aposematism and capture tolerance may be associated. One explanation is that a high degree of capture tolerance facilitates the evolution of post detection (“secondary”) defences and associated warning signals. However perhaps a more likely scenario is that a high capture tolerance is selected for in defended species, especially if conspicuous, because if they can survive for long enough to reveal their defences then they may be released unharmed. Alternatively, both capture tolerance and secondary defences may arise through independent or joint selection, with both traits subsequently facilitating the evolution of conspicuous warning signals. Whatever its ultimate cause, the three-way association appears widespread and has several key implications, including inhibiting the evolution of automimicry and shaping the evolution of tactile mimicry. Finally, we present a range of research questions and describe the challenges that must be overcome in developing a more critical understanding of the role of capture tolerance in the evolution of anti-predator defences.