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Environment and mate attractiveness in a wild insect

Citation

Tregenza, Tom; Niemelä, Petri; Rodríguez-Muñoz, Rolando; Hopwood, Paul (2022), Environment and mate attractiveness in a wild insect, Dryad, Dataset, https://doi.org/10.5061/dryad.0cfxpnw5h

Abstract

The role of female choice in sexual selection is well established, including the recognition that females choose their mates based on multiple cues. These cues may include intrinsic aspects of a male’s phenotype as well as aspects of the environment associated with the male. The role of the spatial location of a potential mate has been well studied in territorial vertebrates. However, despite their role as laboratory models for studies of sexual selection, the potential for insects to choose their mates on the basis of location has scarcely been studied. Here, we use a natural population of individually tagged crickets (Gryllus campestris) to examine how the pairing success of males can be predicted by the burrow(s) they occupy, independent of their own identity. We use observations of the entire breeding season over ten independent years to provide replication of our analysis and to determine whether the relative importance of these factors is stable across years. We find that both male identity and the identity of the burrow at which he is present affect the likelihood that he is paired with a female, but the burrow has a consistently greater influence across years. Furthermore, the two factors interact: the relative attractiveness of an individual male depends on which burrow he occupies. Our finding demonstrates a close interaction between naturally and sexually selected traits. It also demonstrates that mate choice studies may benefit from considering not only obvious secondary sexual traits, but also more cryptic traits such as microhabitat choice. Keywords: sexual selection, attractiveness, territory, burrow, Orthoptera, mate choice. 

Methods

We have monitored the population of G. campestris in our meadow in northern Spain (see WildCrickets.org)  since 2006 (Makai et al., 2020; Rodríguez-Muñoz et al., 2019b; Rodríguez-Muñoz et al., 2019c; Rodríguez-Muñoz et al., 2010).  These field crickets have a single annual generation; nymphs of both sexes dig burrows in the autumn and overwinter in them, emerging to resume foraging and growth in early spring (Rodríguez-Muñoz et al., 2011). The first adults appear in our meadow in late April, and a few days after becoming adult, males begin to call by rubbing their forewings together. This calling attracts females (Zuk and Simmons, 1997), but males also move around the meadow (Rodríguez-Muñoz et al., 2019d) encountering conspecifics at burrows where adults of both sexes spend the vast majority of their time.  Both sexes compete for burrows: when two members of the same sex meet at a burrow, either one of them immediately leaves, or there is a fight, which is followed by the loser leaving.  When members of the opposite sex meet at a burrow, fights are very rare; normally either one of them leaves, or the pair begin to cohabit at the burrow, frequently mating repeatedly during this period (Rodríguez-Muñoz et al., 2011).  After an average of 0.64 ± 1.44 days (Rodríguez-Muñoz et al., 2019d), one of the pair moves to a different burrow.  Males show no signs of attempting to prevent females from leaving, suggesting that females remaining at a burrow with a male are choosing to do so.  Both sexes typically have multiple mating partners throughout their lives (Rodríguez-Muñoz et al., 2010).  Burrows that are not occupied by a cricket are rapidly taken over by other invertebrates such as spiders and ants; typically an unoccupied burrow will be unrecognisable as a burrow within a few days and re-occupation of such sites by a cricket is very unusual.  Similarly, burrows do not persist from one breeding season to the next.

We record information about the behaviour of adult crickets by searching for burrows at least weekly from February each year until the end of the breeding season, when the last adult cricket dies, sometime in July.  Each burrow is flagged with a unique number. A few days after emerging as an adult, we trap every individual at their burrow and glue a plastic tag onto their pronotum.  The tag has a unique 1-2 character code allowing them to be visually identified.  By mid to late April, usually before the adults start to emerge, we install up to 133 infrared day/night cameras.  The cameras use motion activated digital video recording software (i-Catcher, i-codesystems.co.uk), to continuously record the activity around the entrance to each burrow and store these video recordings on servers housed in a building adjacent to the meadow.  Because the number of occupied burrows is sometimes greater than the number of cameras, we carry out direct daytime observations of burrows that lack a camera every 1-2 days. We record the ID of any adult present or whether a nymph is in residence. This allows us to accurately record adult emergence dates, even if burrows are not directly monitored by video at that particular time (last instar nymphs and recently emerged adults rarely move among burrows, so the presence of an adult where there was a nymph the day before indicates an emergence).  Our analysis covers the years 2006-2016 with the exception of 2014 (we had not completed detailed video watching for 2014 at the point when the analysis for this study was carried out).

Usage Notes

File is .csv.  We are keen to collaborate in exploiting these data so if you have an idea about how to use them please contact us and we can provide lots of additional information.

Funding

Natural Environment Research Council, Award: NE/E005403/1, NE/H02364X/1, NE/L003635/1 and NE/R000328/1