Mate Preference Plasticity in a Critically Endangered Frog: Implications for Conservation Breeding

Abstract

Variation in female mate preferences for male traits remains poorly understood (both among and within females), despite having important evolutionary and conservation implications, particularly for captive breeding. Here, we investigate female mate preferences for male advertisement call frequency, and determine whether preferences vary over repeated trials, in the critically endangered southern corroboree frog, Pseudophryne corroboree. We conducted a series of phonotaxis trials in a six-speaker arena where naïve, captive-bred, virgin females were offered a choice between low, average and high frequency male advertisement calls, with a subset of females tested repeatedly. In the first trial, we found no evidence for a population-level preference for call frequency, but females spent less time in the low call zone than expected by chance. However, our results showed that female mate preferences changed over sequential trials. Females spent significantly more time in the low frequency call zone in the third trial compared to the first trial, and, in the last trial, females exhibited a significant population-level preference for low frequency calls. Subsequently, repeatability estimates of female preferences were low and did not significantly deviate from zero. Our results indicate that female P. corroboree mate preferences can exhibit temporal variation, and suggest that females are more attracted to low call frequencies after repeated exposure. These findings imply that female P. corroboree may become choosier over time, and highlight the potential for mate preferences to exhibit phenotypic plasticity within a single reproductive cycle. Overall, these findings provide the first information on mate preferences in P. corroboree, and emphasize the importance of considering individual variation in mate choice studies. From a conservation perspective, knowledge of individual variation in female mate preferences may be used to conduct behavioral manipulations in captivity that facilitate the breeding of genetically valuable individuals, and improve the success of conservation breeding programs.

Multiple phenotypic traits predict male mating success in a critically endangered frog

“…Males with low-frequency calls had higher mating and fertilization success than males with high-frequency calls (irrespective of call rate), a pattern that is relatively common in anurans (Wells 2007;Lesbarrères et al 2008). This outcome suggests that P. corroboree males with low-frequency calls are highly attractive and is in line with the results of our recent manipulative phonotaxis study, which found that P. corroboree females significantly preferred low-frequency male advertisement calls (Kelleher et al 2021b). Our findings strongly suggest that call frequency is an honest signal of male fertility and fertilization potential, as males with low call frequencies also had high fertilization success.…”

“…It is possible that female P. corroboree may weigh call rate more heavily when assessing males with higher call frequency or shorter calls, as opposed to when call frequency is low (which is likely highly attractive and an indicator of male quality) or when call duration is long (as this may act as a hyper stimulus). It is important to consider that patterns of female mate choice observed here could also reflect amongindividual variation in female preferences for particular traits (e.g., some females prefer high call frequency while others prefer low frequency) (Jennions et al 1995); however, our recent manipulative phonotaxis study in P. corroboree did not provide any evidence for among-individual variation in preferences for call frequency (Kelleher et al 2021b). Female mate choice decisions could also reflect variation in how females' weight multiple male attributes (e.g., females assess and combine information from multiple traits but some females weight call rate more heavily while others weight duration more heavily) (Castellano and Rosso 2007), or variation in investment strategies (e.g., level of investment in mate sampling) (Jennions and Petrie 1997;Rosenthal 2017).…”

“…While P. corroboree males do have a distinct territorial call, these appear to function in establishing spacing between males at the time when choruses are first established, with no evidence that resident males suppress advertisement calling by their neighbors (suggestive of a dear enemy effect). A recent, preliminary investigation into female mate preferences in P. corroboree suggested that male dominant call frequency may be important in mate evaluation (Kelleher et al 2021b); however, females may use a suite of different traits to assess potential mates. Advancing our understanding of factors that influence mate choice in P. corroboree may provide conservation managers with knowledge needed to develop behavior-based captive breeding strategies, which may maximize colony reproductive output and population viability.…”