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opencc-zeroDec 2015View details →

Data from: Genetic and morphological evidence of a geographically widespread hybrid zone between two crocodile species, Crocodylus acutus and Crocodylus moreletii

Hybrid zones represent natural laboratories to study gene flow, divergence and the nature of species boundaries between closely related taxa. We evaluated the level and extent of hybridization between Crocodylus moreletii and C. acutus using genetic and morphological data on 300 crocodiles from 65 localities. To our knowledge, this is the first genetic study that includes the entire historic range and sympatric zone of the two species. Contrary to expectations, Bayesian admixture proportions and maximum likelihood estimates of hybrid indexes revealed that most sampled crocodiles were admixed and that the hybrid zone is geographically extensive, extending well beyond their historical region of sympatry. We identified a few geographically isolated, non-admixed populations of both parental species. Hybrids do not appear to be F1s or recent backcrosses, but rather are more likely later-generation hybrids, suggesting that hybridization has been going on for several to many generations and is mostly the result of natural processes. C. moreletii is not the sister species of C. acutus, suggesting that the hybrid zone formed from secondary contact rather than primary divergence. Non-admixed individuals from the two species were distinguishable based on morphological characters, whereas hybrids had a complex mosaic of morphological characters that hinders identification in the wild. Very few non-admixed C. acutus and C. moreletii populations exist in the wild. Consequently, the last non-admixed C. moreletii populations have become critically endangered. Indeed, not only the parental species but also the naturally occurring hybrids should be considered for their potential conservation value.

FIGURE 2 in Environmental correlates of the European common toad hybrid zone

FIGURE 2 Two-species 'global' distribution model for Bufo toads in western Europe. The colour scale runs from deep red for B. spinosus (Pb is zero) to deep blue for B. bufo (Pb at unity). The interrupted black line represents the center of the species' hybrid zone from molecular data, as in fig. 1. Outlined circular windows are those for which model fit is less than good (AUC <0.8, windows 1, 6–8 and 14–16).

FIGURE 3 in Environmental correlates of the European common toad hybrid zone

FIGURE 3 Two regions in the common–spined toad hybrid zone where the mutual species border appears to coincide with rivers. Coloured dots indicate toad populations with nuclear genetic species identifications as Bufo bufo (Q = Pb> 0.5, blue symbols) and B. spinosus (Q = Pb <0.5, red symbols). Open dots have Q-values in the 0.2–0.8 range. For numerical detail see supplementary table S1. Base map figure credits as in fig. 1. A) central France where the species border appears to coincide with the northern- most sections of the Loire (windows 5 and 6) and the upper stretches of the Cher (windows 7 and 8). B) southeastern France where the species border coincides with the Rhône and the lower Isère river at window 13. Note the paucity of data for the high Alps at windows 15 and 16 (see also Lescure and de Downloaded from Brill.com 12/12/2023 03:07:30PM Massary, 2012; Arntzen et al., via2017Open). Access. This is an open access article distributed under the terms of the CC-BY 4.0 License. https://creativecommons.org/licenses/by/4.0/

FIGURE 1 in Environmental correlates of the European common toad hybrid zone

FIGURE 1 Western Europe with France and adjacent countries in Mercator projection. Colours from green to brown indicate increasing altitudes. The Bufo bufo versus B. spinosus mutual range delineation is based upon molecular genetic data, in which the smooth interrupted line is derived by linear interpolation whereas the more angular line is based upon Dirichlet cells (for details see text). The small bodied common toad B. bufo occurs to the northeast and the large bodied spined toad B. spinosus to the southwest of the mutual range border. Environmental data were gathered for 17 overlapping and adjoining circular windows positioned over the mutual range border. Here shown are window 1 in the northwest of France, window 17 in the northwest of Italy and windows 5, 9 and 13 in between. The two boxed areas are highlighted in fig. 3. The base map was downloaded from MapsLand at https://www.mapsland.com, under a Creative Commons Attribution-ShareAlike 3.0 Licence. The animal drawings are by Bas Blankevoort, Naturalis Biodiversity Center.

FIGURE 4 Average values for eight environmental variables over 17 windows that follow the Bufo bufo – B in Environmental correlates of the European common toad hybrid zone

FIGURE 4 Average values for eight environmental variables over 17 windows that follow the Bufo bufo – B. spinosus hybrid zone from the Atlantic coast (window 1) to the Mediterranean (window 17). Variables shown are those selected by a logistic regression analysis, with 'species' as dependent variable and explanatory variables available for selection as in table 1. Units are as in table 1; see also Hijmans et al. (2005). Values for B. bufo and B. spinosus are shown by small and large dots, respectively. Grey areas indicate that values for B. bufo are lower than for B. spinosus. The graph at the top left provides AUC model fit values along with major topographical references. Rectangles indicate stretches of the species contact for which the environmental models have good fit (AUC> 0.8), with consistent results indicated by green shadings. For the other windows with less than good model fit, signals are likely to be absent or void, either from poor sampling (window 1), the presence of rivers (windows 5–9, 13–14), or a thin or absent species' contact (windows 16–17) (see fig. 3).

opencc-by-4.0Nov 2024View details →

Data from: Genomic and bioacoustic variation in a midwife toad hybrid zone: a role for reinforcement?

This data package includes the following datasets and scripts used in the corresponding publication:  <ul> <li>An alignment (fasta format) of the 16S sequences obtained fromt the 221 new A. obstetricans/almogavarii samples barcoded in this study + the A. cisternasii sequence used as outgroup (16S_alignment.fas).</li> <li>A matrix of 1,642 SNPs genotyped in 89 A. obstetricans/almogavarii samples used for ancestry analyses (n89p41r0.5wrs_1642SNP_STRUCTURE.str).</li> <li>The R script used to compute geographic clines with HZAR and their graphical displays (Cline_analyses.r) and the input files it uses (Transect_Q_mtDNA_HZAR.csv; Transect_n57p19r0.5_diag_loci_HZAR.csv; dist_transect.txt; clines_diag_SNPs_1perlocus.csv).</li> <li>The R script used for the bioacoustic analyses (Alytes_FR_Bioacoustics.r) and the corresponding input data extracted from 71 mating calls of A. obstetricans/almogavarii (Alytes_FR_Bioacoustics.csv) the R script used for their analysis.</li> </ul>

opencc-zeroDec 2021View details →

Introgression between Sphyrapicus nuchalis and S. varius sapsuckers in a hybrid zone in west-central Alberta

Studying species interactions at hybrid zones allows biologists to understand the forces that promote speciation. Hybridization among Sphyrapicus nuchalis, S. varius, and S. ruber has long been acknowledged, and hybrid zones between S. nuchalis/S. ruber and S. varius/S. ruber have been characterized with both genetic and genomic data. Using a combination of next-generation Restriction Site-Associated DNA sequencing (RAD-Seq) and traditional genetic methods, we examined patterns of introgression in the poorly characterized S. nuchalis/S. varius contact zone; the two most similar species in the complex, though they are not each other's closest relatives. We found high introgression rates, with several early and many advanced generation hybrids along a 275 km stretch of Rocky Mountain foothill, pointing to a well-established hybrid zone with hybrid individuals backcrossing with individuals from the parental species and each other. Plumage colouration in the hybrid zone was a relatively poor indicator of parental or hybrid status, which could be attributed to the possible involvement of few large effect genes.

opencc-zeroMay 2022View details →

Asymmetric song recognition does not influence gene flow in an emergent songbird hybrid zone

Hybrid zones can be used to examine the mechanisms affecting reproductive isolation and speciation, like song. Song has equivocal support as a driver of speciation; we did not find song to cause reproductive isolation. We examined an emerging secondary contact zone between White-crowned Sparrow subspecies pugetensis and gambelii by measuring song variation, song recognition, plumage, morphology and mtDNA. Plumage and morphological characters provided evidence of hybridization in the contact zone, with some birds possessing plumage and song characteristics intermediate between the subspecies. Playback experiments revealed asymmetric song recognition: male pugetensis displayed greater response to their own song than gambelii song, whereas gambelii did not discriminate significantly. If female choice operates similarly to male song discrimination, we predicted asymmetric gene flow, resulting in a greater number of hybrids with gambelii mitochondrial DNA (mtDNA). Contrary to our prediction, more gambelii and putative hybrids in the contact zone possessed pugetensis mtDNA haplotypes, possibly due to greater pugetensis abundance and female-biased dispersal.

opencc-zeroOct 2022View details →

The gut microbiome reflects ancestry despite dietary shifts across a hybrid zone

The microbiome is critical to an organism's phenotype, and its composition is shaped by, and a driver of, eco-evolutionary interactions. We investigated how host ancestry, habitat, and diet shape gut microbial composition in a mammalian hybrid zone that occurs across an ecotone between distinct vegetation communities. We found that habitat is the primary determinant of diet, while host genotype is the primary determinant of the gut microbiome—a finding further supported by intermediate microbiome composition in first generation hybrids. Despite these distinct primary drivers, microbial richness was correlated with diet richness, and individuals that maintained higher dietary richness had greater gut microbial community stability. Both relationships were stronger in the relative dietary generalist of the two parental species. Our findings show that host ancestry interacts with dietary habits to shape the microbiome, ultimately resulting in the organismal phenotypic plasticity that host-microbial interactions allow.

opencc-zeroOct 2022View details →

Limited movement of an avian hybrid zone in relation to regional variation in magnitude of climate change

Studies of natural hybrid zones can provide documentation of range shifts in response to climate change and identify loci important to reproductive isolation. Using a temporal (36–38 years) comparison of the black-capped (Poecile atricapillus) and Carolina (P. carolinensis) chickadee hybrid zone, we investigated movement of the western portion of the zone (western Missouri) and assessed whether loci and pathways underpinning reproductive isolation were similar to those in the eastern portion of the hybrid zone. Using 92 birds sampled along the hybrid zone transect in 2016 and 68 birds sampled between 1978 and 1980, we generated 11,669 SNPs via ddRADseq. These SNPs were used to assess movement of the hybrid zone through time and to evaluate variation in introgression among loci. We demonstrate that the interface has moved ~5 km to the northwest over the last 36–38 years, i.e., at only one-fifth the rate at which the eastern portion (e.g., Pennsylvania, Ohio) of the hybrid zone has moved. Temperature trends over the last 38 years reveal that eastern areas have warmed 50% more than western areas in terms of annual mean temperature, possibly providing an explanation for the slower movement of the hybrid zone in Missouri. Our results suggest hybrid zone movement in broadly distributed species, such as chickadees, will vary between areas in response to local differences in the impacts of climate change.

opencc-zeroJun 2024View details →

Maintenance of a narrow hybrid zone between native and introduced red foxes (Vulpes vulpes) despite conspecificity and high dispersal capabilities

Human-facilitated introductions of nonnative populations can lead to secondary contact between previously allopatric lineages, resulting in either homogenization of the lineages or stable hybrid zones that are maintained by pre-zygotic (e.g., behavioral) or post-zygotic (e.g., reduced hybrid fitness) reproductive barriers. We investigated patterns of gene flow between the native Sacramento Valley red fox (Vulpes vulpes patwin) and an introduced conspecific population of captive-bred (fur-farm) origin in California's Central Valley. Considering their recent divergence (i.e., ~50 kya), we hypothesized that pre-zygotic mechanisms primarily impede gene flow, rather than post-zygotic barriers. Additionally, some genes originating in nonnative foxes may confer higher fitness in the currently human-dominated landscape resulting in selective introgression into the native population. Genetic analysis of 682 red foxes (255 native, 427 nonnative) at both mitochondrial (cytB + Dloop) and nuclear loci (~19,000 SNPs) revealed significantly narrower cline widths than expected under a simulated model of unrestricted gene flow, consistent with the existence of pre- or post-zygotic reproductive barriers. We identified several loci with reduced introgression linked to behavioral divergence in captive bred foxes, which supports pre-zygotic mechanisms as a putative driver of the narrow hybrid zone. Additionally, several loci with elevated gene flow from the nonnative into the native population, were near genes associated with adaptation to human dominated landscapes. Overall, this study contributes to our understanding of hybrid zone dynamics in vertebrates, particularly in the context of species introductions and landscape changes, underscoring the importance of considering multiple mechanisms that may be at play in maintaining lineages at both the species and subspecies level.

opencc-zeroJul 2024View details →

Genetic variability and telomeres: Insights from a tropical avian hybrid zone

Telomere lengths and telomere dynamics can correlate with lifespan, behavior, and individual quality. Such relationships have spurred interest in understanding variation in telomere lengths and their dynamics within and between populations. Many studies have identified how environmental processes can influence telomere dynamics, but the role of genetic variation is much less well characterized. To provide a novel perspective on how telomeric variation relates to genetic variability, we longitudinally sampled individuals across a narrow hybrid zone (n = 127 samples), wherein two Manacus species characterized by contrasting genome-wide heterozygosity interbreed. We measured individual (n = 66) and population (n = 3) differences in genome-wide heterozygosity and, among hybrids, amount of genetic admixture using RADseq-generated SNPs. We tested for population differences in telomere lengths and telomere dynamics. We then examined how telomere lengths and telomere dynamics covaried with genome-wide heterozygosity within populations. Hybrid individuals exhibited longer telomeres, on average, than individuals sampled in the adjacent parental populations. No population differences in telomere dynamics were observed. Within the parental population characterized by relatively low heterozygosity, higher genome-wide heterozygosity was associated with shorter telomeres and higher rates of telomere shortening – a pattern that was less apparent in the other populations. All of these relationships were independent of sex, despite the contrasting life histories of male and female manakins. Our study highlights how population comparisons can reveal interrelationships between genetic variation and telomeres, and how naturally occurring hybridization and genome-wide heterozygosity can relate to telomere lengths and telomere dynamics.

opencc-zeroJan 2024View details →

Linked collectors and determiners for: Occurrences from a study of a changing Lutz spruce (Picea x Lutzii) hybrid zone on the Kenai Peninsula, Alaska.

Natural history specimen data linked to collectors and determiners held within, "Occurrences from a study of a changing Lutz spruce (Picea x Lutzii) hybrid zone on the Kenai Peninsula, Alaska". Claims or attributions were made on Bionomia by volunteer Scribes, <a href="https://bionomia.net/dataset/6b4d1874-734a-4907-b21f-57cf9b99c148">https://bionomia.net/dataset/6b4d1874-734a-4907-b21f-57cf9b99c148</a> using specimen data from the dataset aggregated by the Global Biodiversity Information Facility, <a href="https://gbif.org/dataset/6b4d1874-734a-4907-b21f-57cf9b99c148">https://gbif.org/dataset/6b4d1874-734a-4907-b21f-57cf9b99c148</a>. Formatted as a Frictionless Data package.

Fig. 51 in Hybridization Among Western Whiptail Lizards (Cnemidophorus Tigris) In Southwestern New Mexico: Population Genetics, Morphology, And Ecology In Three Contact Zones

Fig. 51. Electrophoretic phenotypes of proteins of several subspecies of C. tigris. Left. ESTD polymorphism in C. t. septentrionalis. The fluorescent patterns were photographed in ultraviolet light. Right. Banding patterns of PGM2 that distinguish septentrionalis (SEP, genotype cc) from punctilinealis (PUN genotype dd), marmoratus (MAR, genotype dd), and aethiops (genotype dd, not illustrated). Arrows indicate sites of sample application; anode is to the right.

Fig. 49 in Hybridization Among Western Whiptail Lizards (Cnemidophorus Tigris) In Southwestern New Mexico: Population Genetics, Morphology, And Ecology In Three Contact Zones

Fig. 49. The contact region. Horizontal lines represent range of pure punctilinealis (coloration indices of 0–0.1; table 24), and vertical lines pure marmoratus (coloration indices of 0.8–1.0). Sites in between (2–5, 18, 19, 26, and 41–44) represent primarily hybrids (coloration indices of 0.11–0.79).

Fig. 52 in Hybridization Among Western Whiptail Lizards (Cnemidophorus Tigris) In Southwestern New Mexico: Population Genetics, Morphology, And Ecology In Three Contact Zones

Fig. 52. Differences in the tissue distribution of lactate dehydrogenase, a tetramer. Top (six lanes) LDH1 predominates in heart. Bottom (five lanes). Both LDH1 and LDH2 are active in liver and the banding patterns include numerous isozymes composed of subunits of both. Note the fivebanded patterns for LDH1 for heterozygous diploid C. neomexicanus (NEO) and a triploid hybrid (HYB) of neomexicanus × tigris. In the heart tissue, LDH1 genotype ab for neomexicanus, the isozymes approximate activities of 1:4:6:4:1. For the triploid hybrid with genotype aab, the faster migrating isozymes stain most intensely (activities approximate the theoretically expected ratio of 16:32:24:8:1). These patterns are consistent with the origin of the hybrid from a mating between C. neomexicanus (NEO) and C. t. punctilinealis (PUN). Other abbreviations are: UNI, C. uniparens; MAR, C. t. marmoratus. Arrow indicates sites of sample application; anode is to the right.

Fig. 47 in Hybridization Among Western Whiptail Lizards (Cnemidophorus Tigris) In Southwestern New Mexico: Population Genetics, Morphology, And Ecology In Three Contact Zones

Fig. 47. Relationship between body length and number of eggs per clutch in specimens of C. tigris from the contact region. MAR, pure marmoratus; PUN, pure punctilinealis; HYB, hybrids. Data are summarized in table 30 and figure 48.

Fig. 48 in Hybridization Among Western Whiptail Lizards (Cnemidophorus Tigris) In Southwestern New Mexico: Population Genetics, Morphology, And Ecology In Three Contact Zones

Fig. 48. Relationship between body length and number of eggs per clutch (same data as table 30 and fig. 47), showing 95% confidence intervals (broken lines) for each plot. M, pure marmoratus P, pure punctilinealis; H, hybrids.