Spatial Structure and Habitat Variation in a Grasshopper Hybrid Zone

Bridle, Jon R.; Baird, Stuart J. E.; Butlin, Roger K.

doi:10.1111/j.0014-3820.2001.tb00832.x

Cited by 78 publications

(155 citation statements)

References 41 publications

(34 reference statements)

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“…Habitat heterogeneity, strong ecological gradients and niche differentiation are expected to increase species diversity and the probability of coexistence among sister species at the metacommunity scale (Tews et al 2004;Holt 2006;Davies et al 2009). Contact zones, where similar species coexist and hybridize, have long been recognized as natural laboratories of evolution (Bridle et al 2001), and they have been essential in studies addressing a number of hypotheses regarding the evolution and maintenance of species boundaries (Ellison et al 2008;Gay et al 2008). However, the ecology of contact zones is not as well understood (Patten et al 2004).…”

Section: Introductionmentioning

confidence: 99%

“…By and large, the processes responsible for maintenance of hybrid zones have been inferred from their structure (distribution of parental forms and hybrids) and basic ecological affinities of parental species (Ross and Harrison 2002). Published works that have documented the nature of the underlying ecological gradients that determine contact zone structure are relatively limited (for examples, see Bridle et al 2001;Patten et al 2004;Braby and Somero 2006;Blum 2008). Thus, a fundamental question in the ecology of contact zones is how they are structured and if that structure is predictable based on the strength and nature of existing ecological gradients.…”

Section: Introductionmentioning

confidence: 99%

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Ecological and genetic assessment of spatial structure among replicate contact zones between two topminnow species

2011

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The spatial structure of contact zones is often described as disjunct, diffuse or mosaic and presumed to be related to underlying ecological gradients. However, the ecology of contact zones, how they are structured, and if that structure is predictable based on the strength and nature of ecological gradients is unknown. Large spatial scales and the unreplicated nature of many of the best studied contact zones has made it difficult to codify broader ecological patterns. Freshwater stream fish contact zones have the advantage of being potentially replicated with well defined boundaries and predictable linear gradients (river continuum concept). We sampled four replicate topminnow (Fundulus olivaceus and F. notatus) contact zones in Gulf of Mexico drainages. In each, we quantified contact zone spatial structure and the strength of ecological gradients (habitat, physicochemical variables and fish community functional traits). All three types of contact zone structure were represented. Systems with weaker gradients had diffuse contact zones, low species richness and were numerically dominated by generalist species. Rates of hybridization were also variable among systems. There was no hybridization detected in the mosaic zone while hybrids were found at most of the co-occurrence sites in the diffuse and disjunct zones. Overall, local ecology clearly influences contact zone structure and the two species interact in fundamentally different ways in these four systems.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Ecological and genetic assessment of spatial structure among replicate contact zones between two topminnow species

2011

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“…2001; Ross and Harrison 2002; Ross et al. 2008), and this variation has implications for their relative contributions to reproductive isolation.…”

Section: Discussionmentioning

confidence: 99%

“…The geographic scales of endogenous and exogenous selection are concordant in some hybrid zones (Bridle et al. 2001; Grahame et al. 2006), but discordant in others (Ross and Harrison 2002; Ross et al.…”

Section: Discussionmentioning

confidence: 99%

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Ecological differentiation and habitat unsuitability maintaining a ground beetle hybrid zone

Yasuda

Osawa

2015

Ecology and Evolution

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Exogenous selection via interactions between organisms and environments may influence the dynamics of hybrid zones between species in multiple ways. Two major models of a hybrid zone allowed us to hypothesize that environmental conditions influence hybrid zone dynamics in two ways. In the first model, an environmental gradient determines the mosaic distribution at the boundary between ecologically differentiated species (mosaic hybrid zone model). In the second model, a patch of unsuitable habitat traps a hybrid zone between species whose hybrids are unfit (tension zone model). To test these, we examined the environmental factors influencing the spatial structure of a hybrid zone between the ground beetles Carabus maiyasanus and C. iwawakianus using GIS‐based quantification of environmental factors and a statistical comparison of species distribution models (SDMs). We determined that both of the hypothetical processes can be important in the hybrid zone. We detected interspecific differences in the environmental factors in presence localities and their relative contribution in SDMs. SDMs were not identical between species even within contact areas, but tended to be similar within the range of each species. These results suggest an association between environments and species, and provide evidence that ecological differentiation between species plays a role in the maintenance of the hybrid zone. Contact areas were characterized by a relatively high temperature, low precipitation, and high topological wetness. Thus, the contact areas were regarded as being located in an unsuitable habitat with a drier climate, where those populations are likely to occur in patches with limited precipitation concentrated. A comparison of spatial scales suggests that exogenous selection via environmental factors may be weaker than endogenous selection via genitalic incompatibility.

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Structure of a mosaic hybrid zone between the field cricketsGryllus firmusandG. pennsylvanicus

Larson

Becker

Bondra

et al. 2013

Ecology and Evolution

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Hybrid zones provide insight into the nature of species boundaries and the evolution of barriers to gene exchange. Characterizing multiple regions within hybrid zones is essential for understanding both their history and current dynamics. Here, we describe a previously uncharacterized region of a well-studied hybrid zone between two species of field crickets, Gryllus pennsylvanicus and G. firmus. We use a combination of mitochondrial DNA sequencing, morphological data, and modeling of environmental variables to identify the ecological factors structuring the hybrid zone and define patterns of hybridization and introgression. We find an association between species distribution and natural habitat; Gryllus pennsylvanicus occupies natural habitat along forest edges and natural clearings, whereas G. firmus occupies more disturbed areas in agricultural and suburban environments. Hybridization and introgression occur across patch boundaries; there is evidence of substantial admixture both in morphological characters and mtDNA, over a broad geographic area. Nonetheless, the distribution of morphological types is bimodal. Given that F1 hybrids are viable and fertile in the lab, this suggests that strong pre-zygotic barriers are operating in this portion of the hybrid zone.

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Spatial Structure and Habitat Variation in a Grasshopper Hybrid Zone

Cited by 78 publications

References 41 publications

Ecological and genetic assessment of spatial structure among replicate contact zones between two topminnow species

Ecological and genetic assessment of spatial structure among replicate contact zones between two topminnow species

Ecological differentiation and habitat unsuitability maintaining a ground beetle hybrid zone

Structure of a mosaic hybrid zone between the field cricketsGryllus firmusandG. pennsylvanicus

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