In the competition to acquire mates, environmental factors can be important in determining the relative quality of an individual. These aspects of quality are often conveyed through signals used for mate assessment by the most energetically invested sex. In red-backed salamanders, Plethodon cinereus, chemical signals communicate a surprising amount of information, much of which is dependent on the current condition of the sender. One such conditiondependent aspect of information conveyed via chemicals is the quality of the sender's diet, but it is unclear as to whether this information is actively advertised by the sender (i.e., a signal) or simply inferred from food-derived odors (i.e., a cue). The amount of time on different diets required for changes in signaling is also unknown. I examined how quickly gravid female salamanders could detect a difference between the scents of males on high-vs. low-quality diets without fecal cues. The amount of protein present in two known signaling glands (the mental and postcloacal glands) was also measured after experimental feeding. Gravid females were able to infer the differences in male diet quality after only 1 week. Females also responded to the male scents more quickly after differential feeding had begun. High-quality males had significantly more protein present in both signaling glands than low-quality males. This scenario highlights the ongoing interplay between the quality of an individual and its environment, with males actually advertising the status of this relationship as an honest signal for mate assessment.
In many vertebrate mating systems, mate choice evolves when signalling via visual, chemical or auditory traits is an energetically costly process. Selection may favour individuals that can discriminate among potential mates and invest in signalling to mates with particular characteristics. Most commonly, females with costly gametes are thought to be the more selective sex; however, runaway sexual selection can produce elaborate male ornaments and behaviours that are similarly costly to produce, which can lead to male mate choice. In this study, we used behavioural trials to experimentally test male mate choice in a terrestrial salamander, Plethodon shermani. We investigated whether males altered the proportion of time they spent performing a potentially costly courtship display, 'foot dancing', in the presence of females. Specifically, we explored male mate choice in two experiments: (1) measuring how males modified the time they invested in courtship based solely on female reproductive value, and (2) determining whether males varied the amount of time they invested in courting females of varying sizes but similar reproductive value. In the first experiment, we quantified the duration of male courtship displays when males were paired with females of differing levels of fecundity (nongravid, weakly gravid and strongly gravid). Males displayed longest for females of high reproductive value (strongly gravid females) and less for weakly gravid and nongravid females. In the second experiment, we showed that males paired sequentially with different-sized females of similar reproductive values displayed significantly more often to larger females (i.e. male effort positively correlated with female size). In conclusion, male P. shermani are one of the few vertebrates known to modify their display behaviour based on female mate quality, and visual signs, such as size, are likely to provide honest indicators of fitness.
Chemical communication via chemosensory signaling is an essential process for promoting and modifying reproductive behavior in many species. During courtship in plethodontid salamanders, males deliver a mixture of non-volatile proteinaceous pheromones that activate chemosensory neurons in the vomeronasal epithelium (VNE) and increase female receptivity. One component of this mixture, Plethodontid Modulating Factor (PMF), is a hypervariable pheromone expressed as more than 30 unique isoforms that differ between individual males—likely driven by co-evolution with female receptors to promote gene duplication and positive selection of the PMF gene complex. Courtship trials with females receiving different PMF isoform mixtures had variable effects on female mating receptivity, with only the most complex mixtures increasing receptivity, such that we believe that sufficient isoform diversity allows males to improve their reproductive success with any female in the mating population. The aim of this study was to test the effects of isoform variability on VNE neuron activation using the agmatine uptake assay. All isoform mixtures activated a similar number of neurons (>200% over background) except for a single purified PMF isoform (+17%). These data further support the hypothesis that PMF isoforms act synergistically in order to regulate female receptivity, and different putative mechanisms are discussed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.