Biology Letters最新文献

The invasive weed Parthenium hysterophorus has severely disrupted ecosystems worldwide, driven by its persistent seed bank and phytotoxic compounds that suppress surrounding vegetation and negatively impact herbivorous mammals. It is widely assumed that wild ungulates avoid parthenium weed-dominated areas due to its presumed unpalatability and toxicity, but direct evidence is limited. We experimentally tested whether ungulates in an African savanna actively forage on parthenium weed by contrasting herbivore foraging in mechanically cleared and controlled areas using exclosures in parthenium-invaded areas. We also assessed whether reduction in body condition scores was associated with foraging on parthenium weed, and whether herbivory suppresses parthenium weed regrowth. Our experimental results show that ungulates foraged on parthenium rosettes without apparent negative impacts on body condition. Notably, herbivore activity significantly reduced parthenium cover in cleared areas. These findings reveal a previously undocumented potential for leveraging wild ungulate herbivory as a biocontrol mechanism for managing parthenium weed invasions.

Spatial memory is a fundamental cognitive process that allows animals to navigate and interact with their environment effectively. While extensively studied in mammals and birds, the mechanisms underlying spatial cognition in reptiles remain less understood. In this study, we investigated spatial learning and the influence of behavioural lateralization in the common wall lizard (Podarcis muralis). We examined whether lizards could develop short-term spatial memory and whether lateralization affected their navigation in a complex maze. Experimental lizards received 3 days of training without reinforcement, while control lizards had no prior experience. We found that trained lizards learnt to navigate the maze rapidly, reaching a goal shelter faster and more reliably than controls. Additionally, strongly lateralized individuals took longer to reach the goal during training, but this did not impair escape performance once the route had been learned. Our study reports novel evidence on the role of lateralization during spatial exploration in lizards. Lateralization is hypothesized to enhance information processing, but our data suggest no benefit or cost of lateralization after a route was learnt. Our study contributes to a broader understanding of cognitive evolution across vertebrates and emphasizes the importance of reptiles as models for comparative cognition research.

The presence of a soldier caste is a hallmark of the reproductive division of labour. Trematodes reproduce asexually and form a colony in snails, the first intermediate host. Several trematode species produce morphologically and behaviourally specialized soldiers for defending colony members. These soldiers often possess disproportionately large pharynxes, which serve as a weapon for sucking and attacking their enemies. Here, we demonstrate further anatomical and functional specialization in trematode soldiers. We found that Cercaria batillariae HL7 exhibits the reproductive division of labour with reproductive and soldier castes. Transmission electron microscopy (TEM) revealed that the pharynxes of the soldiers were not just larger than those of the reproductives but were covered by a tegument with serrated projections, coupled with thick bundles of radial muscle fibres, consistent with enhancing the role of soldiers in attaching to and sucking on enemies with their mouths and pharynxes. These sucker structures are analogous to those seen in octopuses. The TEM images further revealed that at least some soldiers of C. batillariae lack a germinal mass, suggesting they are at least temporarily sterile. Our study facilitates the understanding of the trematode social system by providing fine-scale structural differences between the reproductive and soldier castes.

Sex differences in thermal tolerance may significantly impact population responses to climate change, yet most studies examining geographic variation in thermal tolerance focus on a single sex. Here, we investigate how males and females might vary in their capacity to tolerate the heat along a latitudinal cline using the Australian water flea, Daphnia carinata. We measured heat knockdown times in males and females using clones of Daphnia from six populations spanning eastern Australia, raised under two acclimation temperatures (20°C and 25°C). Females consistently showed higher thermal tolerances than males, with greater capacity for thermal acclimation. Critically, we discovered that latitudinal clines in thermal tolerance were sex-specific: females showed a much steeper decline in heat tolerance with increasing latitude compared with males. As a result, sexual dimorphism in thermal tolerance was more than twice as large in northern populations compared with southern populations. These results suggest that sex-specific selection, potentially driven by differential habitat use or the female-biased demography of cyclical parthenogenesis, may be driving divergent thermal adaptation between the sexes. Our findings highlight the importance of considering both sexes when predicting population vulnerability to climate change, as sex-averaged estimates may misrepresent the heat tolerance of populations along environmental gradients.

Populations in managed care are valuable resources that complement in situ conservation efforts, but adaptation to captive conditions and other domestication effects present concerns for conservation. Many populations of fish adapted to sulfide springs are highly endemic and imperiled, potentially benefiting from ex situ conservation efforts. However, it is challenging to maintain natural conditions in the laboratory as hydrogen sulfide (H2S) is highly toxic and coincides with severe hypoxia. Here, we tested whether long-term standardized rearing of sulfide spring fishes leads to the loss of H2S and hypoxia tolerances. We compared the tolerances of Poecilia mexicana (Poeciliidae) from sulfidic and non-sulfidic habitats that were reared in the laboratory for 18 years and wild-caught fish from the same sites. Both H2S and hypoxia tolerances were maintained in laboratory-reared fish from the sulfidic habitat. Additionally, fish from a non-sulfidic cave site, evolutionarily derived from a sulfidic population, exhibited higher H2S and hypoxia tolerances than fish from the non-sulfidic surface site. While domestication can lead to the loss of adaptations to extreme environmental conditions, our research indicates this is not a concern in laboratory stocks of P. mexicana, which retained tolerance of H2S and hypoxia despite not experiencing these stressors for approximately 40 generations.

Failures of the lysosome-autophagy system are a hallmark of ageing and many disease states. As a consequence, interventions that enhance lysosome function are of keen interest in the context of drug development. Throughout the biomedical literature, evolutionary biologists have found cases in which challenges faced by humans in clinical settings have been resolved by non-model organisms adapting to wild environments. Here, we used a primary cell culture approach to survey lysosomal characteristics in species of the genus Mus. We found that fibroblasts from M. spretus, a wild Mediterranean mouse, exhibited elevated lysosomal mass and enzyme activity along with reduced activity of β-galactosidase, a classical marker of cellular senescence, compared with those from M. musculus, a related species adapted to human-associated environments. We propose that classic laboratory models of lysosome function and senescence may reflect characters that diverge from the phenotypes of wild mice. The M. spretus phenotype may ultimately serve as a blueprint for interventions that ameliorate lysosomal dysfunction under conditions of stress and disease.

Heatwaves negatively impact behaviour with associated cognitive impairment in humans. A growing body of literature also reports negative effects of heatwaves on cognition in other animals. A larger brain is known to generate enhanced cognitive abilities that may buffer against environmental changes and thereby potentially increase fitness in large-brained individuals. How a larger brain buffers against adverse effects on cognitive abilities induced by thermal stress, such as that experienced during heatwaves, remains unknown. We examined detour problem solving and working memory during an experimental heatwave in guppies artificially selected on brain size with matching differences in neuron number. Overall, detour problem-solving was impaired among guppies during the heatwave, while working memory was unaffected. Large-brained guppies outperformed small-brained guppies in detour problem-solving and working memory in both the heatwave and control temperature treatments. During the heatwave, large-brained guppies exhibited cognitive performance levels comparable to those of small-brained guppies under normal temperature conditions in the detour task. Our study thus suggests that small-brained individuals might have lower fitness also during heatwaves if increased temperature impair cognitive abilities required for survival and reproduction. Furthermore, our results open up the possibility that cognition-driven brain size evolution may have been influenced by abiotic factors.

Millions of animals are killed by vehicles on roads yearly, left mostly to rot, but these unfortunate mortalities may have a benefit to society that is not widely appreciated: they represent a valuable source of animals for study that does not require and could even replace the use of live wildlife. Here, we provide the first literature review to uncover validated uses for roadkill and, in doing so, encourage uptake of this valuable resource. We located 312 studies using roadkill whose aim included purposes other than enumerating or mitigating roadkill. We identified 26 broad-use and 91 specific-use categories of roadkill carcasses. Most common uses included assessing species presence or distribution, assessing parasite, disease or pathogen presence, assessing roadkill as an index of species abundance, describing species diet and lodging specimens in museums. The studies included at least 650 species; mammals dominated the studies, followed sequentially by reptiles, birds, amphibians and invertebrates. We discuss how we might better take advantage of this source of animals for study and highlight limitations and cautions in their use. Given the proven and diverse uses demonstrated in our review, we encourage the scientific community to now (re-)consider roadkill as an ethical alternative to live animal sampling.

Nests are extended phenotypes capable of providing brood protection against predators, and because they are motionless structures, camouflage is expected to emerge. Birds from different families construct a tail of hung materials underneath their nests, which has been hypothesized to be a type of disruptive camouflage, i.e. an appendage that gives a nest a false shape for hindering detection by predators. Predictions of this hypothesis are that for predators that are visually oriented, nests without a tail are easier to detect, yet this hypothesis never received support likely because predator species and other variables were not considered. Here, we compared predation between nests of blue manakins for which tails were maintained or experimentally removed. To avoid the effects of parental movements in predator's attraction, we used real inactive nests with Plasticine eggs. We also controlled for nest site variables and excluded nests depredated by olfactory animals by monitoring nests with infrared camera traps. Predation was 10 times higher in nests without a tail, and tail absence was the only significant variable explaining nest predation. Furthermore, all of the recorded predators were visually oriented. This is the first work confirming the antipredatory adaptive function of avian nest tails, and corroborated the disruptive camouflage hypothesis.