Competitive ability of neotropical Drosophila predicted from larval development times

Abstract

Interspecific competition is a major aspect of the ecology of insect communities exploiting ephemeral and fragmented resources. To generate testable predictions on the role of competition in such communities, information is required about the competitive abilities of the species involved. In this study we test whether larval development time, an important life‐history trait, can be used to predict interspecific competitive ability in neotropical Drosophila species. Based on earlier work, we predicted a negative relationship between larval development time and competitive ability. Pairwise competition experiments were conducted with seven Drosophila species (in all possible combinations) that are known to coexist in central Panama and represent a wide range of larval development times. We used a novel approach to determine experimental densities, standardising total larval food requirements, and thereby increasing the resolution for detecting general traits involved in exploitation competition. The effects of competition were measured by comparing values for three fitness‐related parameters (thorax length, larval survival, and total mass of emerged adults) against their values at two levels of intraspecific competition. The outcomes of the pairwise competition were significantly explained by the differences in larval development times: within species pairs, species with a longer development suffered more from interspecific competition than those with shorter development. It is argued that larval development time is a major determinant of competitive rank order among drosophilid species, allowing testable community‐wide predictions. In addition, this relationship provides a basis for studying the role of life‐history trade‐offs in community‐level processes. Given the generality of the Drosophila biology, development time is expected to play a similar role in other insect communities exploiting ephemeral and fragmented resources.

Faster development does not lead to correlated evolution of greater pre-adult competitive ability in Drosophila melanogaster

“…It was shown earlier that the fast populations have a lower minimum food requirement for pupation ) and a higher carrying capacity ) than the controls. These earlier observations, taken together with the present results, contradict predictions from canonical density-dependent selection theory (MacArthur & Wilson 1967;Roughgarden 1971), as well as the expectation that faster development confers a competitive advantage (Bakker 1969;Borash, Teótonio et al 2000;Krijger et al 2001). A closer examination of the reasons for this apparent contradiction underscores the subtlety of the evolutionary process and the need to be very circumspect in making broad generalizations about what kinds of trait may be expected to evolve under particular selection pressures.…”

“…Moreover, Drosophila larvae also often face high densities and competition for limited food in these ephemeral habitats (Atkinson 1979;Nunney 1990). These observations have shaped a view that adaptation to larval crowding and selection for faster development in Drosophila should yield similar evolutionary outcomes (Partridge & Fowler 1993;Borash, Teótonio et al 2000;Krijger et al 2001). The pattern of correlations between traits within and among species, however, is known to differ for many sets of traits (Schnebel & Grossfield 1988;Fischer et al 2002;Sharmila Bharathi et al 2003).…”

Fitness traits of Drosophila melanogaster (Diptera: Drosophilidae) after long-term laboratory rearing on different diets

“…Also, egg-laying rate and lifetime egg production is maximized when fed on diets with a P : C ratio 1 : 2 and 1 : 4, respectively (Lee et al, 2008). Krijger et al (2001) report that among neotropical Drosophila species, those with a short development had a competitive advantage over those with a long development. In our study, fl ies reared on the carrot diet had a shorter development and dynamics of eclosion than the other four strains.…”

Body size patterns in Drosophila inhabiting a mesocosm: interactive effects of spatial variation in temperature and abundance

“…To distinguish the interactive and main effects expectations, the spatial pattern of body size variation [sum of all thorax lengths, which is also a surrogate for, and perhaps a better measurement of, abundance-see Krijger et al (2001), and mean thorax length per fruit] across the study arena was investigated using spatial autocorrelation (SAAP version 4.3, Wartenberg 1989). Spatial autocorrelation (or spatial dependence) refers to the tendency of spatially distributed variables to be more similar the closer they are to one another, and more dissimilar as the distance between them increases.…”