2External male reproductive structures have received considerable attention as an early-acting support as a common cause of RI, the potential for mismatch of reproductive structures to cause 1 8 RI due to incompatible species-specific tactile cues has not been tested. We tested the 1 9 importance of mechanical and tactile incompatibilities in RI between Enallagma anna and E. 2 0 carunculatum, two damselfly species that diverged within the past ~250,000 years and currently 2 1 hybridize in a sympatric region. We quantified 19 prezygotic and postzygotic RI barriers using 2 2 both naturally occurring and lab-reared damselflies. We found incomplete mechanical isolation 2 3 between the two pure species and between hybrid males and pure species females. Interestingly, where mechanical isolation was incomplete, females showed greater resistance and refusal to 2 5 mate with hybrid or heterospecific males compared to conspecific males, which suggests that 2 6 tactile incompatibilities involving male reproductive structures can influence female mating 2 7 decisions and form a strong barrier to gene flow in early stages of speciation.

External male reproductive structures have received considerable attention as a cause of reproductive isolation (RI), because the morphology of these structures often evolves rapidly between populations. This rapid evolution presents the potential for mechanical incompatibilities with heterospecific female structures during mating and could thus prevent interbreeding between nascent species. Although such mechanical incompatibilities have received little empirical support as a common cause of RI, the potential for mismatch of reproductive structures to cause RI due to incompatible species-specific tactile cues has not been tested. We tested the importance of mechanical and tactile incompatibilities in RI between Enallagma anna and E. carunculatum, two damselfly species that diverged within the past ∼250,000 years and currently hybridize in a sympatric region. We quantified 19 prezygotic and postzygotic RI barriers using both naturally occurring and laboratory-reared damselflies. We found incomplete mechanical isolation between the two pure species and between hybrid males and pure species females. Interestingly, in mating pairs for which mechanical isolation was incomplete, females showed greater resistance and refusal to mate with hybrid or heterospecific males compared to conspecific males. This observation suggests that tactile incompatibilities involving male reproductive structures can influence female mating decisions and form a strong barrier to gene flow in early stages of speciation.

This paper is dedicated to Georg Ruppëll, in honor of his 75th birthday and with great appreciation for his dedication to capturing the stunning beauty of odonates on film.Genetically determined color polymorphisms have a long history in the study of evolutionary change acting on populations. The Odonata exhibit relatively high levels of sex-specific color polymorphisms in mature adults. In Ischnura and Coenagrion, female-specific polymorphisms are known to be controlled by Mendelian genes. Nearly half of Enallagma species have polymorphic females, but the inheritance of any has yet to be determined. Our aims here were to determine: (1) the inheritance of the color polymorphism in E. hageni; and (2) inherent reproductive characteristics of blue female andromorphs and green heteromorphs reared under controlled conditions as tenerals. Maternal morphs, which developed normal coloration in field enclosures within a week, did not differ in copulation time or clutch size, and their offspring did not differ in sex ratio or survivorship to emergence. Surprisingly, no laboratory-reared offspring developed normal mature coloration. Rather, the initially pale parts of the thorax and abdomen, that normally would turn either blue or green, became melanized. Black novel phenotypes also developed in adults of E. civile, E. anna, E. carunculatum, and E. annexum that as larvae or teneral adults were reared to sexual maturity under greenhouse conditions that differed from the laboratory conditions used to rear E. hageni. We hypothesize that the phenotypic plasticity in body coloration documented in Enallagma results from the quality of UV radiation experienced as a sexually immature adult, which is known to affect melanization in other insects. These examples in Enallagma offer insights into the origin of color novelty in Odonata.

Habitat selection is a basic aspect of the ecology of many species, yet often the term is conflated or confused with both habitat preference and habitat use. We argue that each term fits within a conceptual framework that can be viewed in Bayesian terms and demonstrate, using long-term data on occupancy patterns of a grassland grouse, how prior probability profiles can be estimated. We obtained estimates by specifically focusing on whether and to what extent the Lesser Prairie-Chicken (Tympanuchus pallidicinctus) avoids anthropogenic features such as roads, powerlines, petroleum wells, fences, and buildings, in two study areas, one with denser and one with sparser incidence of features. Grouse strongly avoided large features such as outbuildings and tended to avoid tall features such as powerlines; by contrast, grouse did not or only slightly avoided low, unobtrusive features such as fences. We further examined co-location of pairs of anthropogenic features and found that certain features were avoided so strongly that avoidance distance may be shorter for other features; that is, birds were “pushed toward” some features because they are “pushed away” from others. In each case, our approach points toward a means to incorporate avoidance behavior directly into analytic studies of habitat selection, in that data on use (the posterior, as it were) could be used to infer the selection process provided data on preference (the prior, as it were) could be obtained.