The trade‐off between investment in weapons and fertility is mediated through spermatogenesis in the leaf‐footed cactus bug Narnia femorata

Abstract

Males have the ability to compete for fertilizations through both precopulatory and postcopulatory intrasexual competition. Precopulatory competition has selected for large weapons and other adaptations to maximize access to females and mating opportunities, while postcopulatory competition has resulted in ejaculate adaptations to maximize fertilization success. Negative associations between these strategies support the hypothesis that there is a trade‐off between success at pre‐ and postcopulatory mating success. Recently, this trade‐off has been demonstrated with experimental manipulation. Males of the leaf‐footed cactus bug Narnia femorata use hind limbs as the primary weapon in male–male competition. However, males can drop a hind limb to avoid entrapment. When this autotomy occurs during development, they invest instead in large testes. While evolutionary outcomes of the trade‐offs between pre‐ and postcopulatory strategies have been identified, less work has been done to identify proximate mechanisms by which the trade‐off might occur, perhaps because the systems in which the trade‐offs have been investigated are not ones that have the molecular tools required for exploring mechanism. Here, we applied knowledge from a related model species for which we have developmental knowledge and molecular tools, the milkweed bug Oncopeltus fasciatus , to investigate the proximate mechanism by which autotomized N . femorata males developed larger testes. Autotomized males had evidence of a higher rate of transit amplification divisions in the spermatogonia, which would result more spermatocytes and thus in greater sperm numbers. Identification of mechanisms underlying a trade‐off can help our understanding of the direction and constraints on evolutionary trajectories and thus the evolutionary potential under multiple forms of selection.

Bacterial and fungal components of the gut microbiome have distinct, sex-specific roles in HawaiianDrosophilareproduction

“…Precursors supplied by bacteria may be incorporated into the biosynthesis of sperm membranes. Alternatively, energy stores could be shunted from spermatogenesis or accessory gland protein production to support other physiological needs such as immune defense (Fedorka et al, 2004;Gupta et al, 2013;McKean & Nunney, 2001;Schwenke et al, 2016), telomere length (indicator of aging and lifespan) (Elisa et al, 2023) and defensive weapons (Cavender et al, 2021).…”

Tradeoffs explain scaling, sex differences, and seasonal oscillations in the remarkable weapons of snapping shrimp (Alpheus spp.)

“…One hypothesis called the handicap principle suggests that sexual traits are costly, and these costs ensure that trait expression is not arbitrary. Costly traits lower fitness by reducing survival ( Kotiaho et al, 1998 ; Moller and de Lope, 1994 ; Mappes et al, 1996 ) or reproduction ( Cavender et al, 2021 ; Joseph et al, 2018 ; Moczek and Nijhout, 2004 ; Somjee et al, 2018 ). Individuals should therefore express traits at a level that maximizes their benefits relative to their unit of cost ( Grafen, 1990a ; Grafen, 1990b ; Nur and Hasson, 1984 ; Zahavi, 1977 ).…”

Tradeoffs and Benefits Explain Scaling, Sex Differences, and Seasonal Oscillations in the Remarkable Weapons of Snapping Shrimp (Alpheus spp.)

“…One hypothesis called the handicap principle suggests that sexual traits are costly, and these costs ensure that trait expression is not arbitrary. Costly traits lower fitness by reducing survival (Kotiaho et al, 1998;Møller & de Lope, 1994;Mappes et al, 1996) or reproduction (Cavender et al, 2021;Joseph et al, 2018;Moczek & Nijhout, 2004;Somjee et al, 2018). Individuals should therefore express traits at a level that maximizes their benefits relative to their unit of cost (Grafen, 1990a(Grafen, , 1990bNur & Hasson, 1984;Zahavi, 1977).…”