The best of both worlds: no apparent trade-off between immunity and reproduction in two group-living African mole-rat species

Abstract

Co-operatively breeding mammals often exhibit a female reproductive skew and suppression of the subordinate non-breeding group members. According to evolutionary theory and the immunity–fertility axis, an inverse relationship between reproductive investment and survival (through immunocompetence) is expected. As such, this study investigated if a trade-off between immunocompetence and reproduction arises in two co-operatively breeding African mole-rat species, namely the Damaraland mole-rat ( Fukomys damarensis ) and common mole-rat ( Cryptomys hottentotus hottentotus ), which possess female reproductive division of labour. This study also attempted to investigate the relationship between the immune and endocrine systems in Damaraland mole-rats. There was no trade-off between reproduction and immunocompetence in co-operatively breeding African mole-rat species, and in the case of the Damaraland mole-rats, breeding females (BFs) possessed increased immunocompetence compared with non-breeding females (NBFs). Furthermore, the increased levels of progesterone possessed by Damaraland mole-rat BFs compared with NBFs appear to be correlated to increased immunocompetence. In comparison, BF and NBF common mole-rats possess similar immunocompetence. The species-specific differences in the immunity–fertility axis may be due to variations in the strengths of reproductive suppression in each species. This article is part of the theme issue ‘Evolutionary ecology of inequality’.

Mechanisms of equality and inequality in mammalian societies

“…[39,40]). Because the diversity and evolution of reproductive inequality across humans and other mammals has recently been characterized elsewhere [40] and reproductive skew is discussed extensively in other contributions in this special issue [16,19,41], the first section of this paper focuses on social dominance as a measure of inequality. Social dominance reflects how individuals are organized into a dominance hierarchy based on the outcomes of pairwise agonistic interactions (e.g.…”

“…Humans regularly challenge these sources of inequality through food sharing, peacekeeping, inequity aversion and forgiveness. Inequality also characterizes many animal societies from mole rats [16], hyaenas [17] and mongooses [18] to chimpanzees [19] across the tree of life [20][21][22], but the evolutionary forces shaping inequality across species have received far less attention.…”

Toward an evolutionary ecology of (in)equality

“…Although any of the three forms of wealth noted above can be transmitted to descendants, material forms are generally more successfully inherited. These can include arable land, livestock, durable goods, resource patches, burrows, food caches, nesting sites and the like, as discussed in several papers in this issue [12][13][14]20,27,28]. However, embodied wealth such as skills or knowledge passed down from parents [27] or parental investment in offspring condition [29,30] can be important as well, contributing to developmental origins of inequality [30].…”

“…B 378: 20220287 structured variation we define as inequality [89]. The varied forms and dynamics this can take are amply covered in various papers in this issue [7,11,13,20,21,31,32].…”

“…Although human populations do certainly exhibit reproductive skew [50], extreme forms of reproductive suppression and altruism such as in mole rats [20] and social insects [51] have little human counterpart. One key difference in the human case is attributed to enhanced paternity certainty and resultant paternal investment, resulting in a major expansion of kinship ties and the option of patrilineal as well as matrilineal networks and inheritance pathways [27,28,52,53].…”