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Mating with another species is often maladaptive because it generally results in no or low-fitness offspring. When hybridization is sufficiently costly, individuals should avoid mating with heterospecifics even if it reduces their ability to mate with high-quality conspecifics that resemble heterospecifics. Here, we used spadefoot toads, Spea multiplicata, to evaluate whether females alter their preferences for conspecific male sexual signals (call rate) depending on heterospecific presence. When presented with conspecific signals against a background including both conspecific and heterospecific signals, females preferred male traits that were most dissimilar to heterospecifics—even though these signals are potentially associated with lower-quality mates. However, when these same females were presented with a background that included only conspecific signals, some females switched their preferences, choosing conspecific signals that were exaggerated and indicative of high-quality conspecific mates. Because only some females switched their preferences between these two chorus treatments, there was no population-level preference for exaggerated conspecific male signals in the absence of heterospecifics. These results show that hybridization risk can alter patterns of mate choice and, consequently, sexual selection on male signals. Moreover, they emphasize that the strength and expression of reproductive barriers between species (such as mate choice) can be context-dependent.
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Female chorus frogs delay mate choice under suboptimal environmental conditions
Many traits important for reproductive isolation are environmentally responsive. However, most studies examining reproductive isolation do not explicitly take into consideration environmental variation. Temperature can have a particularly large effect on reproductive behaviours, especially in ectotherms. Here, we tested whether temperature affects the degree of reproductive isolation between the upland chorus frog, Pseudacris feriarum, and its congener Pseudacris nigrita. These two species engage in costly hybridization in nature, leading to reinforcement of male signals and female preferences in sympatry. However, male advertisement calls vary with temperature such that the difference between the advertisement calls of the two species is narrower at cold temperatures than at warm temperatures. To examine the effect of temperature on reproductive isolation in this system, we performed six binary choice preference trials using sympatric female P. feriarum. In these experiments, we acclimated females to either warm (20 °C) or cool (10 °C) temperatures and gave them a choice between heterospecific and conspecific advertisement calls appropriate for the temperature. We also conducted experiments where we gave females a choice between more similar stimuli at warm temperatures to test whether females have narrower preferences at cold temperatures. We found that females always had a significant preference for the conspecific advertisement call, regardless of temperature or signal similarity. However, females took twice as long to make a choice in suboptimal conditions. This time delay may lead to increased risk of hybridization, despite females’ ability to discriminate between calls. Our results highlight the importance of considering environmental context when examining traits involved in reproductive isolation.
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- Award ID(s):
- 2121058
- PAR ID:
- 10499899
- Publisher / Repository:
- Animal Behaviour
- Date Published:
- Journal Name:
- Animal Behaviour
- Volume:
- 209
- Issue:
- C
- ISSN:
- 0003-3472
- Page Range / eLocation ID:
- 215 to 226
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1016/j.anbehav.2023.11.012
