We used adults of the butterfly Eumaeus toxea for two purposes-description of male territorial behavior and investigation of whether body size and muscle fat reserves correlated with social status (resident or intruder) and the probability of winning a territorial contest in dyadic encounters. Males perched in places near cycads (Zamia furfuracea), where females lay eggs. Resident males (those with faithfulness to the same site for several days) used two types of flight of different duration, short (ca. 5 s) and long (ca. 17 s), against male conspecifics. Because of this difference the latter were regarded as true contests. Males that copulated were residents and were also larger than males not observed in copulation. Residents and winners of contests were larger and fatter than intruders (males entering the site that faced a resident with a long-lasting flight) and losers of contests, respectively, possibly because these last two categories of male were individuals with already exhausted energy stores. Body size and fat reserves seemed to correlate with status for resident and intruder males but not for winner and loser males. This possibly means that body size reflects male energy condition. This is supported by the fact that large, resident males are confronted in short contests, in contrast with small, resident males. Our study suggests that the role of size and fat reserves during contests cannot be discounted in butterflies.

The hypothesis that sexual traits reveal the oxidative stress resistance of their bearers has been widely tested in vertebrates but remains unexplored in invertebrates. Here, Hetaerina americana was used to test whether oxidative stress defences are advertised by male wing spot size and colour (a male sexual trait). To this end, we investigated (1) whether oxidative stress reduced survival, (2) whether wing spot size revealed males’ antioxidant defences and (3) how wing spot size and colour were affected by oxidative stress. We elevated oxidative stress by injecting adult males with paraquat (PQ, a compound that favours the production of free radicals) and then examined how this affected male survival and wing spot size. We then related the expression of wing spot size to indicators of oxidative stress—hydrogen peroxide (H2O2) and total antioxidant capacity (TAC), super oxide dismutase (SOD) and catalase (CAT)—in adult males (whose wing spot is fixed) injected with PQ. In teneral males, whose wing spots are still forming, we compared wing spot size, colour (red and yellow chroma) and brightness in individuals injected with PQ or water as a control. Oxidative stress reduced the survival of adult and teneral males. While the H2O2 and TAC markers of antioxidant defences were positively correlated with wing spot size, there was no correlation with CAT and a negative correlation with SOD. In teneral males, PQ increased the yellow chroma and brightness of wing spots, but did not affect spot size or red chroma. Our results highlight the importance of measuring different markers as indicators of male oxidative stress defences, and that the sexual signals of invertebrates may reveal the oxidative stress status of their bearers. A http://onlinelibrary.wiley.com/doi/10.1111/1365-2435.13051/suppinfo is available for this article.

In invertebrates, it has recently been reported that secondary sexual characteristics (SSCs) reflect the antioxidant defense of their bearers, but it is not known what physiological link maintains the honesty of those signals. Here, we used the damselfly Hetaerina americana to test whether juvenile hormone plays such a role. First, we analyzed whether oxidative damage is a real threat in natural damselfly populations by examining the accumulation of oxidized guanines as a function of age in males. Then, we injected paraquat (a pro-oxidant agent) and added the juvenile hormone analog methoprene (JHa) to the experimental group and the JHa vehicle (acetone) to the control group, to determine whether JHa increases the levels of pro-oxidants and antioxidants. We found that DNA oxidation increased with age, and that levels of hydrogen peroxide and superoxide dismutase, but not catalase or glutathione, were elevated in the JHa group compared with the control group. We propose that juvenile hormone is a mediator of the relationship between SSCs and antioxidant capacity and, based on the literature, we know that JHa suppresses the immune response. We therefore suggest that juvenile hormone is a molecular mediator of the general health of males, which is reflected in their SSCs.

Species introductions and extirpations are key aspects of aquatic ecosystem change that need to be examined at large geographic and temporal scales. The Pánuco Basin (Eastern Mexico) has high ichthyological diversity and ecological heterogeneity. However, freshwater fish (FWF) introductions and extirpations since the mid-1900s have modified species range and distribution. We examine changes in FWF species composition in and among four sub-basins of the Pánuco by comparing fish collection records pre-1980 to 2018. Currently, the FWF of the Pánuco includes 95 species. Fishes in the Poeciliidae, Cyprinidae, and Cichlidae, respectively, comprised most records over time. Significant differences in species composition were found between the first (pre-1980) and last (2011–2018) study periods, but not for periods in-between. Eight independent species groups were key for explaining changes in Pánuco river ichthyofauna; one group was dominated by invasive species, and saw increases in the number of records across study periods (faunal homogenization). Another group was formed by species with conservation concern with a declining number of records over time. Thirteen (2 native and 11 non-native) species were responsible for temporal turnover. These results strongly suggest high rates of differentiation over time (via native species loss) following widespread non-native species introductions.