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Accordingly, using paleontological and morphological evidence, Grimaldi and Engel (2005) estimated an 80-to 90-Ma corbiculate bee diversification.has been considered of early Cenozoic origin (Williams, 1985) based on early fossils described under the genus from the Paleocene and Oligocene, but these fossils have since been considered incorrectly or unreliably placed (Engel, 2001; Zeuner and Manning, 1976; Rasnitsyn and Michener, 1991).Radiations are estimated in both Nearctic and Neotropical regions at ∼ 6 to 8 Ma and after 3.5 Ma, concordant with the opening of land corridors between the continents.has resulted in relatively well-defined species, with descriptions of currently accepted species plateauing over 50 years ago (Williams, 1998).The distributions of the species are also relatively well documented and encompass a wide geographic range across the cool temperate and cold regions of the Holarctic and beyond, including Eurasia, North America, Africa north of the Sahara, and much of South America (Williams, 1998).Although distributional patterns of extant bumble bees suggest possible scenarios for historical biogeography and fossil evidence provides approximate dates for these events, estimation of the ancestral biogeographic distributions of (e.g., Plowright and Stephen, 1973; Ito, 1985; Williams, 1985, 1994; Pedersen, 2002; Cameron and Williams, 2003; Kawakita et al., 2004; Hines et al., 2006).Using dated phylogenies, fluctuations in the rate of diversification can be visualized by plotting the log of the number of lineages accumulating across time (Nee et al., 1992, 1994).

A recently published molecular phylogeny of bumble bees provides uniquely comprehensive species sampling for exploring historical patterns of distribution and diversification.A simplified subgeneric system for the bumble bees upon the 38 subgenera employed here and in Cameron et al. The sequence data include ∼ 3745 amplified nucleotides, including both intron and exon regions from five genes: mitochondrial 16S r DNA, elongation factor-1α F2 copy (EF-1α), long-wavelength rhodopsin (opsin), arginine kinase (Arg K), and phosphoenolpyruvate carboxykinase (PEPCK).Missing species are mostly from the mountains of Asia and fall rather evenly across the subgenera (Cameron et al., 2007), with the exception of (5 of 12 species missing).In this article, I examine the historical biogeography of bumble bees using the comprehensive species phylogeny of Cameron et al. Patterns of dispersal are placed in an environmental context using divergence time estimates derived from fossil and ecological information and molecular rates from the literature.The nearly complete species sampling also provides an appropriate framework to make reliable assessments of temporal patterns of diversification, which are analyzed for various clades of interest using LTT plots and diversification statistics, with the stability of these results tested across a body of nearly optimal trees and using a slightly modified data set.

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