Life Sciences Commons^™

Genomic Plasticity And Rapid Host Switching Can Promote The Evolution Of Generalism: A Case Study In The Zoonotic Pathogen Campylobacter, Dan J. Woodcock, Peter Krusche, Norval J. C. Strachan, Ken J. Forbes, Frederick M. Cohan, Guillaume Meric, Samuel K. Sheppard

Frederick M. Cohan

Taxonomy And Phylogeny Of The Asphondylia Species (Diptera: Cecidomyiidae) Of North American Goldenrods: Challenging Morphology, Complex Host Associations, And Cryptic Speciation, Netta Dorchin, Jeffrey Joy, Lukas Hilke, Michael Wise, Warren Abrahamson

Warren G. Abrahamson, II

Reproductive isolation and speciation in herbivorous insects may be accomplished via shifts between host-plant resources: either plant species or plant organs. The intimate association between gall-inducing insects and their host plants makes them particularly useful models in the study of speciation. North American goldenrods (Asteraceae: Solidago and Euthamia) support a rich fauna of gall-inducing insects. Although several of these insects have been the subject of studies focusing on speciation and tritrophic interactions, others remain unstudied and undescribed. Among the latter are at least seven species of the large, cosmopolitan gall midge genus Asphondylia Loew (Diptera: Cecidomyiidae), the taxonomy and biology …

Convergent Evolution Of Behavior In An Adaptive Radiation Of Hawaiian Web-Building Spiders, Todd Blackledge, Rosemary Gillespie

Todd A. Blackledge

Species in ecologically similar habitats often display patterns of divergence that are strikingly comparable, suggesting that natural selection can lead to predictable evolutionary change in communities. However, the relative importance of selection as an agent mediating in situ diversification, versus dispersal between habitats, cannot be addressed without knowledge of phylogenetic history. We used an adaptive radiation of spiders within the Hawaiian Islands to test the prediction that species of spiders on different islands would independently evolve webs with similar architectures. Tetragnatha spiders are the only nocturnal orb-weaving spiders endemic to the Hawaiian archipelago, and multiple species of orb-weaving Tetragnatha co-occur …

Reconstructing Web Evolution And Spider Diversification In The Molecular Era, Todd Blackledge, Nikolaj Scharff, Jonathan Coddington, Tamas Szuts

Todd A. Blackledge

The evolutionary diversification of spiders is attributed to spectacular innovations in silk. Spiders are unique in synthesizing many different kinds of silk, and using silk for a variety of ecological functions throughout their lives, particularly to make prey-catching webs. Here, we construct a broad higher-level phylogeny of spiders combining molecular data with traditional morphological and behavioral characters. We use this phylogeny to test the hypothesis that the spider orb web evolved only once. We then examine spider diversification in relation to different web architectures and silk use. We find strong support for a single origin of orb webs, implying a …

Herbert W. Conn: Formative Decades Of Microbiology And Evolutionary Biology, Frederick M. Cohan, Alexa Boesel

Frederick M. Cohan

Herbert W. Conn (1859–1917) made outstanding contributions to both microbiology and evolutionary biology, reflecting his intellectual command of several biological disciplines. Conn endeavored to make the unseen world of microbes familiar, real, and consequential to members of the general public. He presciently considered the role of bacteria in our own bodies, describing them as being both harmful and beneficial to our health. He also contributed to our understanding of the concept of species, how they originate, and what those ideas might mean in terms of bacterial speciation. In Conn’s spirit, microbial ecologists studying speciation eschew the “species” taxa of bacterial …

Correspondence About "Evolutionary Relationships Among The North American Mallards", Allan R. Phillips, Paul A. Johnsgard

Paul Johnsgard

The confusing leading article of the 1961 Auk calls for comment. Despite his title, "Evolutionary Relationships among the North American Mallards," the author discusses primarily geographic distributions, population sizes, egg-white proteins( !), and certain behavioral patterns. Maps are based on ". . . the literature, personal communications, and the major United States collections," " . and from additional sight and specimen records available to me"; yet only two museums other than Cornell University are mentioned in the acknowledgments. These maps show many records of platyrhynchos far to the south; sometimes (Figure 1) the reader must search hard for any hint …

Using Historical Dna To Characterize Hybridization Between Baltimore Orioles (Icterus Galbula) And Bullock's Orioles (I. Bullockii), Matthew Carling, L. G. Serene, I. J. Lovette

Matthew Carling

Studies of genetic variation across hybrid zones have demonstrated that the evolutionary dynamics within them are often complicated. Using DNA extracted from toe pads of 701 individuals collected by Sibley and Short (1964) about 50 years ago from across the Icterus bullockii-I. galbula hybrid zone, we calculated mitochondrial cline shape parameters and compared them with plumage-based inferences of the hybrid-zone structure. Genetic and hybrid index score clines, estimated from populations collected along the Platte River in Nebraska, were both concordant (equal widths) and coincident (same center). More generally, the proportion of I. bullockii haplotypes within a sampling locality was strongly …

A New Species Of The Red Crossbill (Fringillidae: Loxia) From Idaho, Craig Benkman, J. W. Smith, P. C. Keenan, T. L. Parchman

Craig Benkman

The Red Crossbill (Loxia curvirostra complex) endemic to the South Hills and Albion Mountains in southern Idaho has coevolved in a predator-prey arms race with the lodgepole pine (Pines contorta latifolia). The resulting divergent selection has favored a sedentary, locally adapted crossbill population whose size and vocalizations differ from those of co-occurring Red Crossbills of other call types. It has also led to high levels of reproductive isolation between the "South Hills crossbill" and nomadic taxa with different vocalizations that move in and out of the area yearly. Genetic analyses of amplified fragment length polymorphisms (AFLP) indicate that about 5% …

Does Niche Divergence Accompany Allopatric Divergence In Aphelocoma Jays As Predicted Under Ecological Speciation?: Insights From Tests With Niche Models, John Mccormack, Amanda Zellmer, L. Knowles

John E. McCormack

The role of ecology in the origin of species has been the subject of long-standing interest to evolutionary biologists. New sources of spatially explicit ecological data allow for large-scale tests of whether speciation is associated with niche divergence or whether closely related species tend to be similar ecologically (niche conservatism). Because of the confounding effects of spatial autocorrelation of environmental variables, we generate null expectations for niche divergence for both an ecological-niche modeling and a multivariate approach to address the question: do allopatrically distributed taxa occupy similar niches? In a classic system for the study of niche evolution—the Aphelocoma jays—we …

Speciation In The Highlands Of Mexico: Genetic And Phenotypic Divergence In The Mexican Jay (Aphelocoma Ultramarina), John Mccormack, A. Peterson, E. Bonaccorso, Thomas Smith

John E. McCormack

The pine-oak woodlands of the Mexican highlands harbour significant biological diversity, yet little is known about the evolutionary history of organisms inhabiting this region. We assessed genetic and phenotypic differentiation in 482 individuals representing 27 populations of the Mexican jay (Aphelocoma ultramarina) — a widespread bird species of the Mexican highlands — to test whether populations in the central and northern Mexican sierras display discrete breaks between groups, which would be consistent with a role for the different mountain chains in divergence and speciation. We found abrupt breaks in mitochondrial DNA (mtDNA; ND2 and control region) delineating four major genetic …

Recent Postglacial Range Expansion Drives The Rapid Diversification Of A Songbird Lineage In The Genus Junco, Borja Milá, John Mccormack, Gabriela Castañeda, Robert Wayne, Thomas Smith

John E. McCormack

Pleistocene glacial cycles are thought to have played a major role in the diversification of temperate and boreal species of North American birds. Given that coalescence times between sister taxa typically range from 0.1 to 2.0 Myr, it has been assumed that diversification occurred as populations were isolated in refugia over long periods of time, probably spanning one to several full glacial cycles. In contrast, the rapid postglacial range expansions and recolonization of northern latitudes following glacial maxima have received less attention as potential promoters of speciation. Here we report a case of extremely rapid diversification in the songbird genus …

Genetics Of Interspecific Hybridization In The Triseriatus And Zoosophus Groups Of The Aedes (Protomacleaya) (Diptera: Culicidae)., David B. Taylor

David B. Taylor

Interspecific hybridization was used to examine the genetics of species divergence and phylogeny of mosquitoes in the Triseriatus and Zoosophus groups of Aedes (Protomacleaya). Aedes zoosophus Dyar & Knab exhibited a relatively high degree of reproductive compatibility with Triseriatus group species. Crosses between A. zoosophus and A. triseriatus (Say) produced fertile female and sterile, intersex, male progeny. Crosses between A. zoosophus females and A. brelandi Zavortink males were sterile with no egg embryonation observed. Crosses between A. zoosophus males and A. brelandi females and reciprocal crosses between A. zoosophus and A. hendersoni (Cockerell) produced sterile, intersex female and …

Genetic Compatibility Of Aedes (Protomacleaya) Triseriatus With A. (P.) Brelandi And A. (P.) Hendersoni (Diptera: Culicidae)., David B. Taylor

David B. Taylor

Interspecific hybridization was used to examine reproductive compatibility of Aedes (Protomacleaya) triseriatus (Say) with Aedes (P .) brelandi Zavortink and Aedes (P.) hendersoni Cockerell. Most male progeny were sterile intersexes when A. brelandi or A. hendersoni males were crossed with A. triseriatus females. Female hybrids, and males from the reciprocal crosses, were morphologically normal and fertile. Varying percentages of intersex males were observed among progeny when normal F₁ hybrids were crossed to either parental species or with other hybrids. Egg and female sterility resulting from a partial incompatibility between A. triseriatus cytoplasm and …

Unidirectional Reproductive Incompatibility Between Aedes (Protomacleaya) Brelandi And A. (P.) Hendersoni (Diptera: Culicidae)., David Taylor, George Craig

David B. Taylor

Forced mating was used to determine reproductive compatibility between two species in the Triseriatus Group of Aedes (Protomacleaya). In the cross between A. hendersoni Cockerell females and A. brelandi Zavortink males, only 7% of the females laid eggs that developed embryos. Furthermore, <5% of the eggs from single-female clutches in which one or more eggs did embryonate were fertile. In the reciprocal cross, A. brelandi females crossed to A. hendersoni males, 70% of the females laid fertile eggs and >80% of the eggs from those females became embryonated. Approximately 80% of the females were inseminated in both of the reciprocal crosses. No chromosomal abnormalities were observed in the hybrids. Incompatibility between the A. brelandi male genome and the A. …

Speciation In The Aedes Triseriatus Species Complex., David B. Taylor

David B. Taylor

Interspecific hybridization was used to determine the genetic relationships between the four species of mosquitoes in the Triseriatus and Zoosophus groups of the aedine subgenus Protomacleaya (Diptera : Culicidae) . Four factors were investigated : 1) fertility of intra- and interspecific crosses, 2) morphology of the interspecific hybrids and the genetic bases of morphological characters, 3) modes of postcopulatory reproductive isolation and 4) types of chromosomal changes occurring during and subsequent to the divergence of the species .

Hybrid progeny were produced in 11 of the 12 possible crosses between the four species . Only the Aedes zoosophus female X …