GENETIC DIFFERENTIATION IN THE FLORIDA SUBSPECIES OF HELIANTHUS DEBILIS (ASTERACEAE)

Techniques of horizontal starch gel electrophoresis were employed to estimate levels of genetic variation within and genetic differentiation among populations of the three Florida subspecies of Helianthus debilis. The subspecies are H. d. debilis, H. d. vestitus, and H. d. tardiflorus. These taxa are very similar with respect to levels of genetic variability. The average values across all populations for proportion of polymorphic loci (25.5%) and number of alleles per polymorphic locus (2.35) are comparable to those found in other outcrossing plants. The average frequency of heterozygotes per locus (0.05) is lower than that found in other outcrossers. Local populations within each subspecies are genetically very similar. The average genetic distance between local populations is D = 0.010 ± 0.001. Subspecies vestitus and subspecies tardiflorus are also genetically very similar (D = 0.015 ± 0.001). However, subspecies debilis is differentiated from both subspecies vestitus (D = 0.121 ± 0.006) and subspecies tardiflorus (D = 0.103 ± 0.005). This genetic differentiation parallels morphological differentiation. The average genetic distance among all three subspecies is D = 0.080 ± 0.003. A moderate amount of genetic differentiation accompanies the process of subspeciation in Helianthus debilis.     

Population genetic structure of a widespread coniferous tree, Taxodium distichum [L.] Rich. (Cupressaceae), in the Mississippi River Alluvial Valley and Florida

Studies of genetic variation can elucidate the structure of present and past populations as well as the genetic basis of the phenotypic variability of species. Taxodium distichum is a coniferous tree dominant in lowland river flood plains and swamps of the southeastern USA which exhibits morphological variability and adaption to stressful habitats. This study provides a survey of the Mississippi River Alluvial Valley (MAV) and Florida to elucidate their population structure and the extent of genetic differentiation between the two regions and sympatric varieties, including bald cypress (var. distichum) and pond cypress (var. imbricatum). We determined the genotypes of 12 simple sequence repeat loci totaling 444 adult individuals from 18 natural populations. Bayesian clustering analysis revealed high levels of differentiation between the MAV and the Florida regions. Within the MAV region, there was a significant correlation between genetic and geographical distances. In addition, we found that there was almost no genetic differentiation between the varieties. Most genetic variation was found within individuals (76.73?%), 1.67?% among individuals within population, 15.36?% among populations within the regions, and 9.23?% between regions within the variety. Our results suggest that (1) the populations of the MAV and the Florida regions are divided into two major genetic groups, which might originate from different glacial refugia, and (2) the patterns of genetic differentiation and phenotypic differentiation were not parallel in this species.     

Major biogeographic barriers in eastern Australia have shaped the population structure of widely distributed Eucalyptus moluccana and its putative subspecies

We have investigated the impact of recognized biogeographic barriers on genetic differentiation of grey box (Eucalyptus moluccana), a common and widespread tree species of the family Myrtaceae in eastern Australian woodlands, and its previously proposed four subspecies moluccana, pedicellata, queenslandica, and crassifolia. A range of phylogeographic analyses were conducted to examine the population genetic differentiation and subspecies genetic structure in E. moluccana in relation to biogeographic barriers. Slow evolving markers uncovering long term processes (chloroplast DNA) were used to generate a haplotype network and infer phylogeographic barriers. Additionally, fast evolving, hypervariable markers (microsatellites) were used to estimate demographic processes and genetic structure among five geographic regions (29 populations) across the entire distribution of E. moluccana. Morphological features of seedlings, such as leaf and stem traits, were assessed to evaluate population clusters and test differentiation of the putative subspecies. Haplotype network analysis revealed twenty chloroplast haplotypes with a main haplotype in a central position shared by individuals belonging to the regions containing the four putative subspecies. Microsatellite analysis detected the genetic structure between Queensland (QLD) and New South Wales (NSW) populations, consistent with the McPherson Range barrier, an east‐west spur of the Great Dividing Range. The substructure was detected within QLD and NSW in line with other barriers in eastern Australia. The morphological analyses supported differentiation between QLD and NSW populations, with no difference within QLD, yet some differentiation within NSW populations. Our molecular and morphological analyses provide evidence that several geographic barriers in eastern Australia, including the Burdekin Gap and the McPherson Range have contributed to the genetic structure of E. moluccana. Genetic differentiation among E. moluccana populations supports the recognition of some but not all the four previously proposed subspecies, with crassifolia being the most differentiated.     

Contrasting genetic structures in sister species of North American scrub-jays

Threatened Florida scrub-jays (Aphelocoma coerulescens breed communally, are restricted to xeric sandy scrub habitat, generally disperse fewer than three territory diameters. Closely related Western scrub-jays (A. californica) do not breed communally, have a broader habitat range, disperse greater distances, and are not threatened. We compared the genetic structure of 445 individuals in 11 populations in Florida with 157 individuals in eight populations of Western scrub-jays. At ten microsatellite loci, Florida had 24 out of 47 total alleles, while Western scrub-jays had 44. The Florida populations were more differentiated (G_ST = 0.048) than were a set of five California populations (G_ST = 0.015). A randomization extension of a Mantel test showed a stronger correlation between geographic and Cavalli-Sforza genetic distances among Western than Florida populations. Neighbour-joining trees clustered Florida populations from the same sandy ridge systems, suggesting that habitat continuity is more important than geographic proximity in allowing gene flow and preventing differentiation. For Western populations, isolation by distance appears to be the major determinant of genetic structure. Our results suggest that contrasting genetic structures may arise between closely related species, as a result of differences in ecology and social system. Conserving extant genetic variation in Florida jays will require maintaining viable populations in each of the major sandy ridge systems.     

Glacial refugia and modern genetic diversity of 22 western North American tree species

North American tree species, subspecies and genetic varieties have primarily evolved in a landscape of extensive continental ice and restricted temperate climate environments. Here, we reconstruct the refugial history of western North American trees since the last glacial maximum using species distribution models, validated against 3571 palaeoecological records. We investigate how modern subspecies structure and genetic diversity corresponds to modelled glacial refugia, based on a meta-analysis of allelic richness and expected heterozygosity for 473 populations of 22 tree species. We find that species with strong genetic differentiation into subspecies had widespread and large glacial refugia, whereas species with restricted refugia show no differentiation among populations and little genetic diversity, despite being common over a wide range of environments today. In addition, a strong relationship between allelic richness and the size of modelled glacial refugia (r² = 0.55) suggest that population bottlenecks during glacial periods had a pronounced effect on the presence of rare alleles.     

Deep phylogeographic break among Octopus variabilis populations in China: Evidence from mitochondrial and nuclear DNA analyses

The genetic structure of marine populations is greatly influenced by the dispersal ability of the organisms, and it is intuitive that a limited dispersal capability would result in greater genetic differentiation. Octopus variabilis is a typical cephalopod species that shows limited dispersal potential, and previous genetic surveys by a mitochondrial DNA analyses revealed high levels of genetic differentiation among its populations, suggesting the existence of cryptic or subspecies. To test this hypothesis, amplified fragment length polymorphisms (AFLPs) and the cytochrome oxidase II (COII) gene sequence were used to re-evaluate the spatial genetic structure of five populations of O. variabilis along the coast of China. Four distinct groups were identified within these five populations: the Dalian + Qingdao, Zhoushan, Wenzhou, and Dongshan groups. A deep genetic break among the Dongshan, Wenzhou, and other two groups were specifically recognized by both genetic markers. A considerable number of distinct alleles for AFLP and a deep divergence of 13.9–19.4% in the COII gene sequences were found among them, suggesting the occurrence of potential cryptic or subspecies of O. variabilis. A genetic structure of isolation by distance was identified in O. variabilis by a Mantel test, with the geographic distance explaining 62% of the variation in genetic differentiation. This result suggests that gene flow is geographically restricted for this species and that limited dispersal may be the main reason for the genetic differentiation among O. variabilis populations. The present results indicate that special care should be taken in future fishery exploitation and conservation efforts for this species and that conservation management should include populations representing all lineages.     

The Role of Geographical and Ecological Factors on Population Divergence of the Neotropical otter <Emphasis Type="Italic">Lontra longicaudis</Emphasis> (Carnivora,Mustelidae)

The geographic distribution of the populations of a species are influenced by the spatial structure of the ecosystems, the environmental factors and the presence of geographic barriers. The Neotropical otter, Lontra longicaudis, is widely distributed throughout the Americas, where a wide range of environmental conditions and geographical features could promote genetic and morphological variation on the three currently recognized subspecies. In this study, we combined phylogeographic, morphometric and environmental niche modelling analyses to examine whether: (1) genetic variation is associated with the presence of barriers to gene flow and/or hydrography; (2) genetic and morphologic variation are associated with environmental variation; and (3) the observed variation in L. longicaudis populations corresponds to the previously defined subspecies. We found strong phylogeographic structure between the northern (L. l. annectens) and the two-southern subspecies (L. l. longicaudis and L. l. enudris), and although shallower, we also detected genetic differentiation between the two South American subspecies. Such genetic differentiation corresponds to the hydrography and to the geographical barriers characteristic of the distributional area of the species. We found a correlation between the shape of the skull and mandible with the environmental variation through the distribution of the species, and we rejected the hypothesis of niche equivalency and similarity between the three identified genetic lineages, suggesting adaptations to different environmental conditions. Our results support that the variation in environmental conditions, in concert with geographical barriers to gene flow and hydrography, have led to population divergence of L. longicaudis along the Neotropics. These results have important taxonomic implications for the species and its conservation.     

Ancestral polymorphisms in genetic markers obscure detection of evolutionarily distinct populations in the endangered Florida grasshopper sparrow (Ammodramus savannarum floridanus)

Genetic analyses of bird subspecies designated as conservation units can address whether they represent units with independent evolutionary histories and provide insights into the evolutionary processes that determine the degree to which they are genetically distinct. Here we use mitochondrial DNA control region sequence and six microsatellite DNA loci to examine phylogeographical structure and genetic differentiation among five North American grasshopper sparrow (Ammodramus savannarum) populations representing three subspecies, including a population of the endangered Florida subspecies (A. s. floridanus). This federally listed taxon is of particular interest because it differs phenotypically from other subspecies in plumage and behaviour and has also undergone a drastic decline in population size over the past century. Despite this designation, we observed no phylogeographical structure among populations in either marker: mtDNA haplotypes and microsatellite genotypes from floridanus samples did not form clades that were phylogenetically distinct from variants found in other subspecies. However, there was low but significant differentiation between Florida and all other populations combined in both mtDNA (FST = 0.069) and in one measure of microsatellite differentiation (theta = 0.016), while the non-Florida populations were not different from each other. Based on analyses of mtDNA variation using a coalescent-based model, the effective sizes of these populations are large (approximately 80,000 females) and they have only recently diverged from each other (< 26,000 ybp). These populations are probably far from genetic equilibrium and therefore the lack of phylogenetic distinctiveness of the floridanus subspecies and minimal genetic differentiation is due most probably to retained ancestral polymorphism. Finally, levels of variation in Florida were similar to other populations supporting the idea that the drastic reduction in population size which has occurred within the last 100 years has not yet had an impact on levels of variation in floridanus. We argue that despite the lack of phylogenetic distinctiveness of floridanus genotypes the observed genetic differentiation and previously documented phenotypic differences justify continued designation of this subspecies as a protected population segment.     

Population structure of red-cockaded woodpeckers in south Florida: RAPDs revisited

Six south Florida populations of the endangered red-cockaded woodpecker (Picoides borealis) were sampled to examine genetic diversity and population structure in the southernmost portion of the species' range relative to 14 previously sampled populations from throughout the species range. Random amplified polymorphic DNA (RAPD) analyses were used to evaluate the populations (n= 161 individuals, 13 primers, one band/primer). Results suggested that south Florida populations have significant among-population genetic differentiation (F_ST= 0.17, P < 0.000), although gene flow may be adequate to offset drift (N_m= 1.26). Comparison of Florida populations with others sampled indicated differentiation was less in Florida (F_ST for all populations = 0.21). Cluster analyses of all 20 populations did not reflect complete geographical predictions, although clustering of distant populations resulted in a significant correlation between genetic distance and geographical distance. Overall, results suggest populations in south Florida, similar to the remainder of the species, have low genetic diversity and high population fragmentation. Exact clustering of distant populations supports the ability of RAPDs to differentiate populations accurately. Our results further support past management recommendations that translocations of birds among geographically proximate populations is preferable to movement of birds between distant populations.     

Weak population genetic differentiation in the most numerous Arctic seabird,the little auk

Quantifying patterns of genetic diversity and differentiation among populations of Arctic birds is fundamental for understanding past and ongoing population processes in the Arctic. However, the genetic differentiation of many important Arctic species remains uninvestigated. Here, phylogeography and population genetics were examined in the worldwide population of a small seabird, the little auk (dovekie, Alle alle)—the most numerous avian species of the Arctic ecosystem. Blood samples or feathers were collected from 328 little auks (325 from the nominate subspecies and 3 from the A. a. polaris) in nine main breeding aggregations in the northern Atlantic and one location from the Pacific Ocean. The mtDNA haplotypes of the two subspecies were not segregated into separate groups. Also, no genetic structure was found within the nominate race based on microsatellite markers. The level of genetic differentiation among populations was low yet significant (mean F _ST = 0.005). Some pairwise F _ST comparisons revealed significant differences, including those involving the most distant Pacific colony as well as among some Atlantic populations. Weak population differentiation following the model of isolation by distance in the little auk is similar to the patterns reported in other high-Arctic bird species, indicating that a lack of distinct genetic structure is a common phenomenon in the Arctic avifauna.     

Subspecies of the Central American Squirrel Monkey (Saimiri oerstedii) as Units for Conservation

The accurate diagnosis of conservation units now typically includes recognition of genetic diversity and unique evolutionary lineages and is necessary to inform the conservation management of endangered species. We evaluated whether the two currently recognized subspecies of the endangered Central American squirrel monkey (Saimiri oerstedii) in Costa Rica are evolutionarily significant units (ESUs) that should be managed separately in conservation efforts. We used previously published sequences of 50 individuals of Saimiri oerstedii for 880 bp of the mtDNA d-loop and genotypes of 244 individuals for 16 microsatellites and conducted novel analyses to characterize genetic differentiation between subspecies of Saimiri oerstedii. We measured sequence differentiation and inferred an intraspecific molecular phylogeny and a haplotype network, and found consistent results supporting statistically significant divergence and reciprocal monophyly between subspecies. A population aggregation analysis also supported Saimiri oerstedii citrinellus and S. o. oerstedii as diagnosably distinct units. These results confirm previous genetic studies with smaller sample sizes and are consistent with other factors including differences in pelage and morphology and divergence at nuclear markers. Conservation managers should manage these subspecies separately to prevent the loss of genetic diversity via artificially induced outbreeding. High levels of genetic diversity may buffer populations against outside extinction pressures, to which Saimiri oerstedii are vulnerable because of their dwindling habitat and small population size.     

Genetic distinctiveness of brown pelicans (<Emphasis Type="Italic">Pelecanus occidentalis</Emphasis>) from the Galápagos Islands compared to continental North America

We examined population differentiation across a substantial portion of the range of the brown pelican (Pelecanus occidentalis) to assess (1) the genetic distinctness of the Galápagos subspecies (P. o. urinator) and (2) genetic differentiation between subspecies that inhabit the coasts of North and Central America (P. o. californicus and P. o. carolinensis). Birds were sampled from coastal California, coastal Florida, and the Galápagos Islands. Using a 957 bp (bp) fragment of the NADH dehydrogenase subunit 2 (ND2) gene, 661 bp of the mitochondrial control region, and eleven microsatellite loci we characterize population genetic differentiation among 158 brown pelicans. The Galápagos subspecies is genetically distinct from the sampled continental subspecies, possessing a unique ND2 haplotype and unique mitochondrial control region haplotypes. Samples from the two continental subspecies all possessed the same ND2 haplotype and shared four mitochondrial control region haplotypes. Bayesian clustering in STRUCTURE placed the Galápagos subspecies in a distinct genetic group with high probability, but could not differentiate the continental subspecies from one another. Estimates of migration rates from BayesAss indicated substantial migration between continental subspecies, but no migration between the Galápagos subspecies and either continental subspecies. There are clearly two Evolutionarily Significant Units within the range of the brown pelican, which warrants conservation attention. Further investigation should determine how the un-sampled subspecies (P. o. murphyi and P. o. occidentalis) fit into the broader picture.     

Evaluating hybridization as a potential facilitator of successful cogongrass (Imperata cylindrica) invasion in Florida,USA

Interspecific hybridization is cited as one potential mechanism for increased invasiveness, particularly among some grass species. In the southeastern United States, the successful invasion of cogongrass (Imperata cylindrica) has sometimes been attributed to hybridization with the previously naturalized Imperata brasiliensis. This research aimed to determine whether genetic signals are consistent with these two species having experienced interspecific hybridization in Florida (USA), where it has been proposed that such an event facilitated cogongrass invasion across the region. Individuals of invasive I. cylindrica populations (n = 66) were sampled broadly from the state, and I. brasiliensis (n = 63) individuals were sampled from expertly identified and vouchered populations in Miami-Dade County. Genetic analysis utilized amplified fragment length polymorphisms in sampled individuals, and failed to detect significant genetic differentiation between the two species. Analysis of molecular variance partitioned the majority of detected variation within populations (86 %), while only 8 % was significantly partitioned between I. cylindrica and I. brasiliensis (F_ST = 0.135, P < 0.001). Both STRUCTURE analysis and principal coordinates analysis strongly indicated the presence of a single genetic group across the sampled populations. Hybrid analysis furthermore failed to support interspecific hybridization. Florida populations thus are suggested to share genetic parent material(s) and/or have experienced substantial admixture across the state. Therefore, this study suggests Imperata populations in South Florida that are currently considered to be I. brasiliensis are not genetically distinct from I. cylindrica, and regional cogongrass invasion likely was not facilitated by previously postulated interspecific hybridization.     

Limited structure and widespread diversity suggest potential buffers to genetic erosion in a threatened grassland shrub Pimelea spinescens (Thymelaeaceae)

Pimelea spinescens is a critically endangered species of the temperate grasslands of southeastern Australia. Two subspecies are recognised. Subspecies, P. spinescens subsp. spinescens, formerly common and widespread, is found in isolated remnants of previously extensive grasslands. The second subspecies, subsp. pubiflora, is thought to have been historically rare with only two geographically-isolated extant populations. The grassland communities exist now as fragmented remnants representing <1 % of their extent prior to European settlement in the early 1800s. Conservation management strategies for species in these critically endangered ecosystems rely on an understanding of genetic diversity and population structure to ensure long-term evolutionary potential. We used chloroplast DNA (cpDNA) and microsatellite markers to examine the population genetic structure of both subspecies. Analysis of cpDNA revealed 14 haplotypes with high divergence between the single haplotype found in subsp. pubiflora and most remaining haplotypes restricted to subsp. spinescens. Microsatellites also indicated high genetic differentiation between subspecies but little evidence of sub-structuring within either subspecies. Results suggest that seed dispersal has not been as limited as previously thought. In this fragmented habitat, a lack of genetic structure suggests buffers to genetic erosion, with current patterns reflecting genetic diversity prior to fragmentation. Plant longevity and the presence of seed banks may contribute to the maintenance of these patterns, resulting in a lag between fragmentation and genetic erosion. Whilst factors such as longevity and seed banks may be preserving historic genetic diversity, management is required to ensure the maintenance of this diversity into the future.     

Phylogeny and biogeography of the Japanese rhinoceros beetle,Trypoxylus dichotomus (Coleoptera: Scarabaeidae) based on SNP markers

The Japanese rhinoceros beetle Trypoxylus dichotomus is one of the largest beetle species in the world and is commonly used in traditional Chinese medicine. Ten subspecies of T. dichotomus and a related Trypoxylus species (T. kanamorii) have been described throughout Asia, but their taxonomic delimitations remain problematic. To clarify issues such as taxonomy, and the degree of genetic differentiation of Trypoxylus populations, we investigated the genetic structure, genetic variability, and phylogeography of 53 specimens of Trypoxylus species from 44 locations in five Asian countries (China, Japan, Korea, Thailand, and Myanmar). Using specific‐locus amplified fragment sequencing (SLAF‐seq) techniques, we developed 330,799 SLAFs over 114.16M reads, in turn yielding 46,939 high‐resolution single nucleotide polymorphisms (SNPs) for genotyping. Phylogenetic analysis of SNPs indicated the presence of three distinct genetic groups, suggesting that the various subspecies could be treated as three groups of populations. PCA and ADMIXTURE analysis also identified three genetic clusters (North, South, West), which corresponded to their locations, suggesting that geographic factors were important in maintaining within population homogeneity and between population divergence. Analyses of SNP data confirmed the monophyly of certain subspecies on islands, while other subspecies (e.g., T. d. septentrionalis) were found to be polyphyletic and nested in more than one lineage. AMOVA demonstrated high level of differentiation among populations/groups. Also, pairwise F_ST values revealed high differentiation, particularly between South and West, as well as between North and South. Despite the differentiation, measurable gene flow was inferred between genetic clusters but at varying rates and directions. Our study demonstrated that SLAF‐seq derived markers outperformed 16S and COII sequences and provided improved resolution of the genetic differentiation of rhinoceros beetle populations from a large part of the species’ range.     

Genetic differentiation and limited gene flow among fragmented populations of New Zealand endemic Hector’s and Maui’s dolphins

Gene flow among small fragmented populations is critical for maintaining genetic diversity, and therefore the evolutionary potential of a species. Concern for two New Zealand endemic subspecies, the Hector’s (Cephalorhynchus hectori hectori) and Maui’s (C. h. maui) dolphins, arises from their low abundance, slow rate of reproduction, and susceptibility to fisheries-related mortality. Our work examined genetic differentiation and migration between the subspecies and among regional and local Hector’s dolphin populations using mitochondrial (mt) DNA and microsatellite genotypes from 438 samples. Results confirmed earlier reports of a single unique mtDNA control region haplotype fixed in the Maui’s dolphin, and provided new evidence of reproductive isolation from Hector’s dolphins (9-locus microsatellite F _ST?=?0.167, P?<?0.001). Independent evolutionary trajectories were also supported for Hector’s dolphin populations of the East Coast, West Coast, Te Waewae Bay and Toetoe Bay. Low asymmetrical migration rates were found among several Hector’s dolphin populations and assignment tests identified five Hector’s dolphins likely to have a migrant father from another regional population. There appears to be sufficient step-wise gene flow to maintain genetic diversity within the East and West Coasts; however, the two local South Coast populations exhibited a high degree of differentiation given their close proximity (~100?km). To maintain the evolutionary potential and long-term survival of both subspecies, genetic monitoring and conservation management must focus on maintaining corridors to preserve gene flow and prevent further population fragmentation and loss of genetic diversity, in addition to maintaining local population abundances.     

Genetic Analysis of the <Emphasis Type="Italic">Indri</Emphasis> Reveals No Evidence of Distinct Subspecies

Subspecies were traditionally defined by identifying gaps between phenotypes across the geographic range of a species, and may represent important units in the development of conservation strategies focused on preserving genetic diversity. Previous taxonomic research proposed that phenotypic variation between scattered Indri indri populations warranted the naming of two distinct subspecies, I. i. indri and I. i. variegatus. We tested these subspecific designations using mitochondrial sequence data generated from the control region or D-loop (569 bp) and a large section (2362 bp) of multiple genes and tRNAs known as Pastorini’s fragment and nuclear microsatellite markers. This study used 114 samples of I. indri from 12 rainforest sites in eastern Madagascar, encompassing the entire range of the species. These genetic samples represent multiple populations from low- and high-elevation forests from both putative subspecies. Molecular analyses of the mitochondrial sequence data did not support the two proposed subspecies. Furthermore, the microsatellite analyses showed no significant differences across the range beyond population level differentiation. This study demonstrates the utility of incorporating multiple lines of evidence in addition to phenotypic traits to define species or subspecies.     

Historical range contraction,and not taxonomy,explains the contemporary genetic structure of the Australian tree <Emphasis Type="Italic">Acacia dealbata</Emphasis> Link

Irrespective of its causes, strong population genetic structure indicates a lack of gene flow. Understanding the processes that underlie such structure, and the spatial patterns it causes, is valuable for conservation efforts such as restoration. On the other hand, when a species is invasive outside its native range, such information can aid management in the non-native range. Here we explored the genetic characteristics of the Australian tree Acacia dealbata in its native range. Two subspecies of A. dealbata have previously been described based on morphology and environmental requirements, but recent phylogeographic data raised questions regarding the validity of this taxonomic subdivision. The species has been widely planted within and outside its native Australian range and is also a highly successful invasive species in many parts of the world. We employed microsatellite markers to investigate the population genetic diversity and structure among 42 A. dealbata populations from across the species’ native range. We also tested whether environmental variables purportedly relevant for the putative separation of subspecies are linked with population genetic differentiation. We found no relationship between population genetic structure of A. dealbata in Australia and these environmental features. Rather, we identified two geographically distinct genetic clusters that corresponded with populations in the northeastern part of mainland Australia, and the southern mainland and Tasmanian range of the species. Our results do not support the taxonomic subdivision of the species into two distinct subspecies based on environmental features. We therefore assume that the observed morphological differences between the putative subspecies are plastic phenotypic responses. This study provides population genetic information that will be useful for the conservation of the species within Australia as well as to better understand the invasion dynamics of A. dealbata.     

Ecotypes and genetic structure of Rhinanthus alectorolophus (Orobanchaceae) in southwestern Germany

European annual species of the genus Rhinanthus often exhibit seasonal ecotypic variation, a phenomenon also known from related genera of hemiparasitic Orobanchaceae. Populations with different flowering times exist, correlated with differences in a number of morphological characters. The present study evaluates the correlation of morphological characters and genetic differentiation of populations of Rhinanthus alectorolophus. Thirty-nine populations of three different subspecies from southwestern Germany were sampled. A total of 798 individuals were used for morphological analyses and 187 of these for AFLP analyses. Principal component analysis showed that morphological variation is mostly continuous. In a discriminant analysis based on morphological characters, only 89.7 % of all individuals were correctly assigned to their previously determined subspecies, indicating that subspecies identification is ambiguous for some populations. Using AFLP data and Bayesian assignment analysis, the sampled individuals could be grouped in three genetic clusters which do not correspond to the three subspecies. Instead, the clustering shows a clear geographic pattern and a Mantel test likewise revealed a significant correlation between genetic and geographic distances. Correlations of genetic distances with differences in morphological characters were weak and mostly insignificant. The results indicate that the subspecies of R. alectorolophus do not form discrete entities and that the character combinations distinguishing them are homoplastic.