Host use and developmental instability in the cactophilic sibling speciesDrosophila gouveaiandD. antonietae

Abstract

The Drosophila repleta group encompasses an ensemble of species that inhabit desertic areas that are inhospitable to other drosophilids. These species have a tractable ecology, as they breed and feed on necrotic tissues of a wide diversity of species of Cactaceae, with a certain degree of host specificity, which makes them suitable models to investigate the role of host plant shifts in diversification. Most species have their own primary host plant, which may be shared with a closely related species. However, the consequences of host plant shifts from primary to secondary hosts have not been thoroughly studied so far. We investigated the effects of the cactus host on developmental instability and performance of D. gouveai Tidon‐Sklorz & Sene and D. antonietae Tidon‐Sklorz & Sene (Diptera: Drosophilidae), a pair of closely related sibling species, and of their F1 interspecific hybrids reared in primary and secondary host plants. Fluctuating asymmetry (FA) for wing size was significantly greater in flies of both species reared in their respective secondary cactus host than in those grown in the primary host. Interspecific hybrids also exhibited host‐dependent levels of FA. However, hybrids did not show greater FA than the parental species, suggesting that hybridization per se did not affect developmental stability. Even though cactus host shifts affected different measures of fitness (larval viability and adult size) both in D. antonietae and D. gouveai, we did not detect a consistent relationship between FA and fitness. Our results suggest that FA cannot be used as a sensitive indicator of genetic and phenotypic quality and we discuss its application as a fitness predictor.

Constant fluctuating asymmetry but not directional asymmetry along the geographic distribution of Drosophila antonietae (Diptera, Drosophilidae)

“…D. antonietae is more viable and has a lower development time when reared in culture media with exudates from the cactus Pilosocereus machrisii Y. Dawson in comparison with media from its own host plant, C. hildmannianus (Soto et al, 2007). On the other hand, the level of FA in the wing of D. antonietae is higher when reared in culture media based on C. hildmannianus than on P. machrisii (Soto et al, 2010). These combined observations might indicate that C. hildmannianus itself could be considered as a stressing factor for the development of D. antonietae.…”

“…The association between different types of asymmetry has been found in the partridge A. chucker (Kark, 2001), where the pattern of size asymmetry changes geographically (from the center to the periphery), such that peripheral populations have higher levels of asymmetry (FA, DA, and AS) than central ones. The relationship between DA and DI has also been suggested for Drosophila by Soto et al (2010) when investigating the development of D. antonietae and Drosophila gouveai Tidon-Sklorz and Sene, 2001 in culture media based on different host cacti (C. hildmannianus and P. machrisii). The presence of DA in wing shape was detected when either species was reared on C. hildmannianus media, but not on P. machrisii (Soto et al, 2010).…”

“…Directional asymmetry is not a rare effect in Diptera Pélabon and Hansen, 2008;Soto et al, 2010), as well in other invertebrate (Graham et al, 1998;Schneider et al, 2003) and vertebrate groups (Kark, 2001;Marchand et al, 2003;Loehr et al, 2013). In Diptera, suggested that the genetic basis of DA has been conserved over evolutionary time due to the existence of a left-right axis determining the position of imaginal disks (developmental precursors of wings) on each side of the body.…”

Analyzing Fluctuating Asymmetry with Geometric Morphometrics: Concepts, Methods, and Applications

“…In experiments with cactus-breeding species of Drosophila, one species had increased fluctuating asymmetry of wing shape in the non-preferred cactus host, but other species showed no difference or even had greater fluctuating asymmetry in the primary host [118,123]. Additional experiments demonstrated that alkaloids in the cactus tissue can cause increased fluctuating asymmetry and abnormal wing phenotypes [119].…”

“…A few studies of shape in Drosophila found no significant directional asymmetry of wing shape [115][116][117][118][119] or mixed results [120][121][122][123][124][125][126], although a series of other studies did find it [15,16,54,56,62,77,85,123]. Similarly, one study on human skulls [127] found no directional asymmetry of shape, whereas several others reported directional asymmetry of the skull [47,68,84,86,90,94,109] and soft tissues of the face and ears [38,66,98,104,105,108].…”