Clinal variation in morphology among eastern populations of the waterstrider, Aquarius remigis Say (Hemiptera: Gerridae)

Abstract

\Ve examined morphological variation among populations of' the stream-dwelling waterstrider, Aquarius rem@. A previous analysis of allnzyme variation along a transect from southern Quchcr to southern North Carolina revealed two distinct 'types' of A . rm&, north and south of a transition zone in southern New York and northern Prnnsylvania. T o assess the conrordanre of morphological and allozyme differentiation, adults were sampled liom 15 populations along thr original transect, as well as I 1 additional populations in New York, Connecticut and New Jersey. Eight measurements of leg and body sizr "ere taken of presewed individuals. Univariate and multivariate analyses (multiple regression, PCA, discriminant analysis) reveal significant difyerentiation between northern and southern populations with a transition zone between latitudes 39" and 42" north. Strong clines within each region and a clear transition between regions support prrvious suggestions that there are two distinct 'types' of' this species in eastern North Amerira. Tiir transition zone in morphology coincides with that rrvealed by the allozynic vaiiation, but extends further south. The covariance of allozyme frequency and morphometric traits suggests that differentiation has occurred through cicariance and secondary contact, and that in this system, cladistic and adaptive differentiation are coupled. ADDITIONAI, KEY WORDS: body size ~ morphology -PCA ~ discriminant analysis transition zone ~ vicariance ~ speciation.

Latitudinal gradient effect on the wing geometry of Auca coctei (Guérin)(Lepidoptera, Nymphalidae)

“…Ray (1960) was one of the pioneers in suggesting that ectothermic invertebrates such as insects also fulfill Bergmann's rule. However, the inverse Bergmann rule has also been suggested for insects (Van Voorhies 1997;García-Barros 2000), stating that for diverse taxa body size decreases from the tropics toward the poles, that is, from warmer to colder climates (Brennan & Fairbairn 1995;Mousseau 1997).…”

When Rensch Meets Bergmann: Does Sexual Size Dimorphism Change Systematically With Latitude?

“…Ectotherms also display converse Bergmann clines, in which body size decreases toward the poles (Park 1949;Brennan and Fairbairn 1995;Mousseau 1997;Ashton 2004;Blanckenhorn and Demont 2004). This effect is clearly mediated by season length rather than temperature: shorter growing seasons at higher latitudes progressively limit the time available for foraging, growth, and development and hence the phenotypic body size that can be attained.…”

A test of Allen's rule in ectotherms: the case of two south American Melanopline Grasshoppers (Orthoptera: Acrididae) with partially overlapping geographic ranges

“…Converse Bergmannian clines are much more frequent in ectotherms than in endotherms, especially in insects (Brennan & Fairbairn 1995, Blanckenhorn & Demont 2004, Bidau & Martí 2007a. Body size in insects probably obeys to different ecophysiological factors and evolutionary pressures than those in endotherms.…”