Data from: Similar preferences for ornamentation in opposite- and same-sex choice experiments

Selection due to social interactions comprises competition over matings (sexual selection stricto sensu) plus other forms of social competition and cooperation. Sexual selection explains sex differences in ornamentation and in various other phenotypes, but does not easily explain cases where those phenotypes are similar in males and females. Understanding such similarities requires knowing how phenotypes influence non-sexual social interactions as well, which can be very important in gregarious animals, but whose role for phenotypic evolution has been overlooked. For example, ‘mate choice’ experiments often found preferences for ornamentation, but have not assessed whether those are strictly sexual or are general social preferences. Using choice experiments with a gregarious and mutually-ornamented finch, the common waxbill (Estrilda astrild), we show that preferences for ornamentation in the opposite-sex also extend to same-sex interactions. Waxbills discriminated between opposite- and to same-sex individuals, but most preferences for colour traits were similar when interacting with either sex. Similar preferences in sexual and non-sexual associations may be widespread in nature, either as social adaptations or as by-product of mate preferences. In either case, such preferences may set the stage for the evolution of mutual ornamentation and of various other similarities between the sexes.

社会互动驱动的选择包含交配竞争（狭义性选择（sexual selection stricto sensu））以及其他各类社会竞争与合作行为。性选择能够解释两性间装饰性状及其他多种表型的差异，却难以解释两性间上述表型趋于一致的情形。要理解这类表型相似性，还需明晰表型如何影响非性相关的社会互动——这一点在群居动物中尤为关键，但其在表型进化中的作用长期被忽视。例如，‘择偶偏好（mate choice）’实验常检测到对装饰性状的偏好，却未评估这类偏好究竟是严格的择偶性偏好，还是一般性的社会偏好。本研究以群居且两性均具装饰性状的雀科鸟类普通蜡嘴雀（Estrilda astrild）为对象开展选择实验，结果表明，对异性装饰性状的偏好同样适用于同性互动场景。普通蜡嘴雀能够区分异性与同性个体，但多数针对色彩性状的偏好，在与异性或同性互动时表现一致。这类在性社交与非性社交中均存在的相似偏好，在自然界中可能广泛存在，其成因既可能是社会适应性演化，也可能是择偶偏好的副产品。无论属于哪种情形，这类偏好都可能为两性装饰性状趋同以及其他多种两性相似性状的演化奠定基础。