Dispersal potential impacts size clines of grasshoppers across an elevation gradient

Abstract

Body size is a life history trait that determines the reproductive success of a variety of organisms. Changes in body size may have a genetic component when persistent conditions such as season length and climate select for individuals of an optimal body size and an environmental component when it is influenced on an ecological scale by factors such as weather, food availability, or maternal effects. Along elevational gradients that experience seasonality, insects commonly become smaller with increases in elevation. In this study we test the hypothesis that dispersal potential, an indicator of gene flow, impacts the type of size clines exhibited by insects along elevational gradients and that these differences in local adaptation should lead to predictable changes in their reproductive potential and output. Using two short winged grasshopper species, Aeropedellus clavatus and Melanoplus boulderensis, and two long winged species, Camnula pellucida and Melanoplus sanguinipes, we showed that species with low dispersal potential are associated with significant declines in body size with increases in elevation while species with high dispersal potential displayed no size clines. Consistent with short winged species being more locally adapted, we show that reproductive potential, as measured by the proportion of ovarioles that become functional, do not differ among populations of short winged species, but decline with elevation in the long winged species. While our study failed to show that dispersal potential impacts reproductive output in a consistent and predictable manner (as measured by clutch and egg sizes), we address the possibility that clutch size may not reflect changes in total reproductive output and that changes in egg size may be a plastic trait. We concluded that studies exploring the evolution of body size, the reproductive capacity and species level responses to environmental change should note the importance of dispersal potential in influencing these patterns.

Elevational differences in developmental plasticity determine phenological responses of grasshoppers to recent climate warming

“…Mean body size in the field does decline with elevation along the gradient for the short-winged species (M. boulderensis), but not for the long-winged species (M. sanguinipes and C. pellucida) [19,20]. Laboratory rearing of M. boulderensis could help assess whether delaying development allows the highelevation populations to reach larger body sizes.…”

Do different rates of gene flow underlie variation in phenotypic and phenological clines in a montane grasshopper community?

“…Our study focuses on a steep environmental gradient near Boulder, Colorado, spanning 2,000 m elevation over a horizontal distance of ~35 km, where Melanoplus boulderen sis and Aeropedellus clavatus, short-winged, early-season species, can be compared to Camnula pellucida and Melanoplus sanguinipes, long-winged, mid to late-season species. Phenotypic clines in morphological, physiological, and reproductive traits have been well documented among these species (Table 1, Figure 1), with notable differences among our four focal taxa corresponding to ecological divergence Levy & Nufio, 2015). The two long-winged species are considered more dispersive, because in addition to occurring at a broader range in elevation, they are occasionally collected as "accidentals" (nonresident migrants) at high-elevation sites along the gradient (Alexander, 1964).…”

“…In the short-winged species, statistically well-supported differences in life-history and physiological phenotypes along this elevational gradient Levy & Nufio, 2015) . In the short-winged species, statistically well-supported differences in life-history and physiological phenotypes along this elevational gradient Levy & Nufio, 2015) .…”

“…Here, we test the hypothesis that clinal differences in growth and reproduction "(life-history traits)" and physiological traits of four ecologically divergent grasshopper species Buckley, Nufio, & Kingsolver, 2014;Levy & Nufio, 2015) are associated with genetic differentiation and reduced demographic estimates of gene flow (local adaptation). We examine a large set of genome-wide single nucleotide polymorphisms for each species to estimate genetic parameters.…”

Vegetation richness, height, coverage and spatial distribution mediate grasshopper abundance in the upper reaches of Heihe River, China

“…Grasshopper needs adequate food resources and habitat to support their survival, development, and reproduction (Levy and Nufio 2015;Wachter 1995). In the study area, the vegetation was dominant by perennial Gramineae and Cyperaceae, and some species have taken strong attraction or indispensable to specific grasshoppers; combining with the influence of the altitude, the community was an appearance in the specific area, such as the altitude from 2500m-2700m was an area of species richness (Fig.1b, Fig.3).…”