No abstract

Many sexually selected ornaments and weapons are elaborations of an animal’s outer body surface, including long feathers, colorful skin, and rigid outgrowths. The time and energy required to keep these traits clean, attractive, and in good condition for signaling may represent an important but understudied cost of bearing a sexually selected trait. Male fiddler crabs possess an enlarged and brightly colored claw that is used both as a weapon to fight with rival males and also as an ornament to court females. Here, we demonstrate that males benefit from grooming because females prefer males with clean claws over dirty claws but also that the time spent grooming detracts from the amount of time available for courting females. Males, therefore, face a temporal trade-off between attracting the attention of females and maintaining a clean claw. Our study provides rare evidence of the importance of grooming for mediating sexual interactions in an invertebrate, indicating that sexual selection has likely shaped the evolution of self-maintenance behaviors across a broad range of taxa.

Eye size influences visual acuity, sensitivity, and temporal resolution and is a result of vertebrate adaptation to the environment. The habitats of snake species are diverse, ranging from fossorial, terrestrial, arboreal, to aquatic. They also demonstrate a variety of behavioral and physiological characteristics, such as activity time, feeding patterns, and prey detection. In this study, we comparatively investigated how the relative eye size (i.e., eye diameter vs. head width) associated with the ecological (i.e., habitat), behavioral (i.e., diel activity pattern, foraging strategy), and physiological traits (i.e., the presence of pits), respectively, across six snake families from Taiwan. Among the traits we examined, we found that terrestrial and/or diurnal snakes tended to exhibit the larger relative eye size, indicating the evolutionary responses of eye size to changes in habitat types and activity patterns, respectively, while no evidence of how foraging strategies and the presence of pits affected snake eye size was found. Our findings not only shed light on the adaptive significance of the visual system in diversifying the behaviors and the environments exploited in snakes, but also underline the interactive effects of multidimensional evolutionary attributes (e.g., behavior, ecology, physiology and phylogeny) on the evolution of optimal visual performance.

The timing of reproduction is critical to reproductive success in many animal species. Parents that can perceive and respond to environmental cues and time the hatching/birth of their offspring to optimal environmental conditions show higher reproductive success. Intertidal ectotherms are under particularly strong selection because larval development rates are temperature-dependent, and larvae must hatch during the highest spring tides to avoid high levels of inshore predation. Here we investigate whether female fiddler crabs, Austruca mjoebergi, can mitigate the effects of high temperatures by adjusting the timing of reproductive events and/or by behavioural compensation. We experimentally manipulated incubation temperatures between 30 and 36 °C, based on natural and predicted temperature conditions, and found that hatching success decreased linearly with increasing temperatures. However, temperature had no effect on the timing of fertilization or hatching, suggesting that larval development rate was not temperature-dependent. Across the tested temperatures, females did not adjust egg size, the amount of yolk in each egg, larvae size or clutch size. In conclusion, high temperatures prevented clutches from reaching the hatching stage, but within the range of temperatures that facilitated hatching, there was no evidence of behavioural compensation and no discernible effect of temperature on reproductive timing.

No abstract

Perceptual biases explain the origin and evolution of female preference in many species. Some responses that mediate mate choice, however, may have never been used in nonmating contexts. In the fiddler crab, Uca mjoebergi, mate‐searching females prefer faster wave rates and leading wave; however, it remains unclear whether such responses evolved in a mating context (i.e., the preference has effect on the fitness of the female and her offspring that arise from mating with a particular male) or a nonmating contexts (i.e., a female obtains direct benefits through selecting the male with a more detectable trait). Here, we compared the preferences of mate‐searching with those of ovigerous females that are searching for a burrow and do not concern about male “quality.” Results showed that as both mate‐searching and ovigerous females preferentially approached robotic males with faster wave rates. This suggests that wave rate increases detectability/locatability of males, but the mating preference for this trait is unlikely to evolve in the mating context (although it may currently function in mate choice), as it does not provide fitness‐related benefit to females or her offspring. Wave leadership, in contract, was attractive to mate‐searching females, but not ovigerous females, suggesting that female preference for leadership evolves because wave leadership conveys information about male quality. We provide not only an empirical evidence of sensory biases (in terms of the preference for faster wave), but the first experimental evidence that mating context can be the only selection force that mediates the evolution of male sexual traits and female preference (in terms of the preference for leading wave).

1. Currently, we lack enough knowledge to fully explain how the impacts of species invasion on native communities are attributed to multifaceted, individual-based behavioural outcomes.2. Here, we illustrate the long-term population dynamics of the native long-tailed sun skink (Eutropis longicaudata) before and after the invasion of the common sun skink (Eutropis multifasciata). We conducted diet investigation, morphological measurement, and a series of behavioural experiments both in the field and laboratory. We explained how the impacts of the invasive skink on the native skink can cascade towards the population level based on these individual-level behavioural data.3. We present evidence of competition exclusion of the native skink population resulting from the invasion of the common sun skink. The drastic decline found in the native skink population was largely accounted for by low recruitment, as shown by the decrease in its clutch numbers correspondingly. 4. We also found dominance of the invasive skink in both exploitation competition and intraguild predation. Considering the highly overlapping morphological and dietary niches between the two species, our findings imply that the native skink has undergone strong food competition and predation pressure on its eggs and juveniles.5. Interestingly, the native skink started to display parental care behaviour 2 years after the invasion event, and its clutch survival rate has recovered since then.The shift in parental care behaviour may help the native skink cope with this new predation pressure from the invasive skink. 6. Overall, the two competitive skinks showed low chances of coexisting. The negative population growth of this native skink species may be primarily derived from poor reproductive performance, given a sharp decline in its clutch numbers and its inferiority in exploitation competition, despite rebounding clutch survival rates.

No abstract