Proceedings of the Royal Society B: Biological Sciences最新文献

Sebecid notosuchians are the only terrestrial crocodyliforms to survive the Cretaceous-Palaeogene extinction, 66 Ma, which eliminated large-bodied species (above approximately 5 kg) in terrestrial ecosystems. Early sebecid evolution is unclear due to the scarcity of remains from both sides of the boundary. We present the stratigraphically earliest post-extinction notosuchian record, from the lower Palaeocene Salamanca Formation of Patagonia. Tewkensuchus salamanquensis n. gen. n. sp. has unique features, including a skull roof with elevated lateral margins, and an accessory peg and socket articulation between the postorbital and posterior palpebral. Our phylogenetic analysis allies Tewkensuchus with a clade of predatorial crocodyliforms from the Eocene of Europe (and possibly of Africa, as Eremosuchus may also belong to this clade). This clade forms the sister taxon of South American sebecids. We name Sebecoidea for this more inclusive clade of Eurogondwanan notosuchians and suggest that its spatial distribution reflects earlier diversification and dispersal events, which are only partially known. We estimate a body mass of around 300 kg for Tewkensuchus, one of the largest known notosuchians. Phylogenetic optimization of notosuchian body size change reconstructs a Cretaceous-Palaeogene boundary-crossing sebecoidean lineage with an estimated mass between 332 and 443 kg. This provides the first support for the survival of a large-bodied terrestrial vertebrate lineage across the K-Pg boundary.

Most hosts contain few parasites, whereas few hosts contain many. This pattern, known as aggregation, is well-documented in macroparasites where parasite intensity distribution among hosts affects host-parasite dynamics. Infection intensity also drives fungal disease dynamics, but we lack a basic understanding of host-fungal aggregation patterns, how they compare with macroparasites and if they reflect biological processes. To begin addressing these gaps, we characterized aggregation of the fungal pathogen Batrachochytrium dendrobatidis (Bd) in amphibian hosts. Utilizing the slope of Taylor's Power law, we found Bd intensity distributions were more aggregated than many macroparasites, conforming closely to lognormal distributions. We observed that Bd aggregation patterns are strongly correlated with known biological processes operating in amphibian populations, such as epizoological phase (i.e. invasion, post-invasion and enzootic), and intensity-dependent disease mortality. Using intensity-dependent mathematical models, we found evidence of evolution of host resistance based on aggregation shifts in systems persisting with Bd following disease-induced declines. Our results show that Bd aggregation is highly conserved across disparate systems and contains signatures of potential biological processes of amphibian-Bd systems. Our work can inform future modelling approaches and be extended to other fungal pathogens to elucidate host-fungal interactions and unite host-fungal dynamics under a common theoretical framework.

Incomplete taxon sampling due to underestimation of present-day biodiversity biases diversification analysis by favouring slowdowns in speciation rates towards the recent time. For instance, in diversification dynamics studies in Crocodylia, long-term low net-diversification rates and slowdowns in speciation rates have been suggested to characterize crocodylian evolution. However, crocodylian cryptic diversity has never been considered. Here, we explore the effects of incorporating cryptic diversity into a diversification dynamics analysis of extant crocodylians. We inferred a time-calibrated cryptic-species-level phylogeny using cytochrome b sequences of 45 lineages compared with the formally recognized 26 crocodylian species. Diversification rate estimates using the cryptic-species-level phylogeny show increasing speciation and net-diversification rates towards the present time, which contrasts with previous findings. Cryptic diversity should be considered in future macroevolutionary analyses; however, the representation of cryptic extinct taxa represents a major challenge. Additionally, further investigation of crocodylian diversification dynamics under different underlying genomic data is encouraged upon advances in population genetics. Our case study adds to the diversification dynamics knowledge of extant taxa and demonstrates that cryptic species and robust taxonomic assessment are essential to study recent biodiversity dynamics with broad implications for evolutionary biology and ecology.

Because temperature has pervasive effects on biological rates, climate warming may alter the outcomes of interactions between insect hosts and their parasitoids, which, for many host species, constitute the single largest source of mortality. Despite growing interest in parasitoid-host responses to climate change, there are few empirical tests of thermal tolerance differences between non-model lepidopteran hosts and their parasitoids and almost none from mountain ecosystems where warming is occurring more rapidly. We examined the thermal ecology of a host-parasitoid interaction in the Rocky Mountains using wild populations of the aspen leaf miner (Phyllocnistis populiella) and a set of previously unknown eulophid parasitoids that attack them. Host and parasitoid development rates were differentially sensitive to temperature. In addition, upper thermal limits of adult parasitoids were lower than those of host caterpillars, and in choice experiments, parasitoids reared at different temperatures showed no plasticity in preferred temperatures. However, when coupled to simulations of leaf microclimates in aspen canopies, these observations suggest, contrary to expectations, that climate warming may potentially benefit parasitoids.

Crop productivity was transformed by incorporating dwarfing genes that made plants smaller and less competitive (more cooperative). Beyond such major shifts in plant size, however, it is not clear how much variation in competitiveness remains and how to find its genetic basis. We performed plant density experiments, using 484 lines of the Arabidopsis thaliana multi-parent advanced generation inter-cross population, to compare methods for mapping the genetic basis of plant competitiveness. We first found that a major dwarfing gene, the erecta allele, caused reduced competitiveness and higher group productivity. Then, measuring competitiveness more generally, we found: (i) extensive variation in generic measures of competitiveness that extended beyond the effects of the erecta allele; (ii) a novel genomic region underlying variation in competitiveness; and (iii) that some measures of competitiveness were more useful than others. Our results show how modern genomic resources, including multi-parent populations, could uncover hidden genes for more cooperative crop plants.

The spatial cognitive abilities of food-storing birds are well documented, but how individual variation in spatial memory influences natural caching behaviour is poorly understood. Here we tested wild toutouwai (Petroica longipes) on two spatial memory tasks and compared their performance with caching decisions. We found that birds with better performance on a spatial reference memory task also travelled further to cache food items. As widely distributed caches are thought to offer protection against cache theft, birds with better reference memories may therefore gain greater benefits from food-storage than birds with poor memories. Females outperformed males in the spatial reference memory task, and performance also declined with age. Birds also displayed marked individual differences in how they interacted with the reference memory task, with some potentially following a heuristic to locate the reward. By contrast, birds showed no evidence that they learned the contingencies of a working memory task. Our results provide empirical evidence that individual variation in spatial memory performance influences the choices that toutouwai make during caching. We recommend that researchers seeking to link cognition and behaviour in the wild take care to select ecologically relevant cognitive tasks that are likely to underpin fitness-linked behaviours targeted by selection.

It has been suggested that in threatening environments, both women and men should prefer more masculine men as romantic and coalition partners, respectively. Empirical evidence for this hypothesis has been weak or inconsistent, primarily because most experimental research has focused on elevating the perceived danger from other men through virtual threats. This study investigates whether personal experience with violence predicts the preference for masculine features in 326 Senegalese participants presented with pairs of manipulated facial photographs of West African men (one more feminine, one more masculine) and asked to indicate which face is more attractive (to women) or more trustworthy (to men). The findings reveal a strong association between violence exposure and facial feature preferences. Those who experienced (particularly physical) violence showed a higher preference for masculinized faces (up to 95% in women, 82% in men) compared to the baseline (57% in women, 63% in men). This difference is proposed to reflect an adaptive strategy of prioritizing physical protection in settings with a higher incidence of violent confrontations. Much of the variance can be found between groups. The direct effect of experienced violence diminishes over time, which suggests a dynamic interplay between innate predispositions and environmental influences on aesthetic preferences.

How phenotypes are shaped by multilevel selection-the theoretical framework proposing natural selection occurs at more than one level of biological organization-is a classic debate in biology. Though social behaviours are a common theoretical example for multilevel selection, it is unknown if and how multilevel selection acts on sociality in the wild. We studied the relative strength of multilevel selection on both individual behaviour and group social structure, quantified with social networks and 19 years of data from a wild, free-living mammal, the yellow-bellied marmot (Marmota flaviventer). Contextual analysis (exploring the impact of individual and group social phenotypes on individual fitness, relative to each other) revealed multilevel selection gradients in specific fitness and life history contexts, with selection for group social structure being just as strong, if not stronger, than individual social behaviour. We also found antagonistic multilevel selection gradients within and between levels, potentially explaining why increased sociality is not as beneficial or heritable in this system compared with other social taxa. Thus, the evolutionary dynamics of hierarchical or nested biological traits should be assessed at multiple levels simultaneously to tell a more accurate and comprehensive story. Overall, we provide empirical evidence suggesting that multilevel selection acts on social relationships and structures in the wild and provide direct evidence for a classic, unanswered question in biology.

Pesticides and pathogens are major drivers of bee declines. However, their potential interactions are poorly understood, especially for non-Apis bees. This study assessed the combined effects of infestation by the honeybee pathogen Vairimorpha ceranae and chronic exposure to the insecticide flupyradifurone on Osmia bicornis and Apis mellifera. We investigated whether V. ceranae could reproduce in a new solitary bee host (O. bicornis) and assessed sublethal and lethal effects of the pathogen and the pesticide, alone and in combination. We also analysed the interactive effects of the combined exposure on V. ceranae proliferation and bee survival in the two bee species. Newly emerged bees were orally infected with 100 000 spores of V. ceranae and then exposed ad libitum to flupyradifurone at field-realistic concentrations. We showed, for the first time to our knowledge, that V. ceranae can replicate in the midgut of O. bicornis, causing histological damage, impaired phototactic response, reduced food consumption and decreased longevity. The pathogen-pesticide combination caused a synergistic effect in O. bicornis, leading to an abrupt survival decline. In A. mellifera, V. ceranae and flupyradifurone showed antagonistic survival effects, but the pesticide promoted pathogen proliferation. Our results warn against the potential effects of pathogen spillover and multiple stressor exposure on non-Apis bees.

Movement is a key part of life for many species. In solitary animals, the energetic costs of movement can be mitigated through energetically efficient strategies that produce faster, straighter movements. However, little is known about whether moving as part of a collective enhances or limits the ability of individual group members to express such strategies. Drawing on 6 years of population-level, high-resolution (1 Hz) GPS tracking of group-living vulturine guineafowl (Acryllium vulturinum), we detected 886 events from 94 tagged individuals where their groups made large, range-shifting displacements in response to changing environmental conditions. We contrasted these movements with data from 94 similarly large displacement events by 19 lone, dispersing individuals. Our results suggest that individuals in groups can significantly reduce their energetic cost of transport when making large displacements (15.3% more efficient relative to their normal daily ranging) by increasing the speed and straightness of their movements. However, even during their most efficient movements, individuals in groups could not achieve or maintain comparable increases in speed to lone individuals, resulting in significantly limited efficiency gains (35.7% less efficient than solitary individuals). Overall, this study provides evidence for a substantial energetic cost arising from collective movement.