Geographic Variation In Morphology Research Articles

GENETIC DIVERGENCE AND DIFFERENTIATION WITHIN THE WESTERN SCRUB-JAY (APHELOCOMA CALIFORNICA)

Abstract Western Scrub-Jays (Aphelocoma californica) range throughout the western United States and Mexico and exhibit substantial geographic variation in morphology and behavior. Western Scrub-Jays are a polytypic species complex with three distinct groups (californica, woodhouseii, and sumichrasti) associated with geography and distinguished by morphology, genetics, and behavior. Until recently, the Island Scrub-Jay (A. insularis) and the Florida Scrub-Jay (A. coerulescens) were considered subspecies within the Western Scrub-Jay complex. We analyzed mitochondrial DNA sequences (control region I) to reveal the phylogenetic relationships within Western Scrub-Jays and used maximum likelihood, a Bayesian approach, and a relaxed phylogenetic approach to construct phylogenies. In addition, we used several methods to estimate divergence time between clades. Our results reveal that the interior woodhouseii group, which contains the sumichrasti subclade, and the coastal californica group have had a long and inde...

Geographic trend in sexual size dimorphism and body size of Osteopilus septentrionalis (Cuban treefrog): implications for invasion of the southeastern United States

We collected Osteopilus septentrionalis from Central Florida for analysis of sexual size dimorphism and compared our data to published information from populations across the native and introduced range of the species. We found significant sexual size dimorphism (females larger), with the degree of dimorphism decreasing with increasing degrees north latitude, a trend largely driven by a pronounced decrease in female mean snout to vent length. Potential explanations for this trend include reduced growth rates, increased time to maturity, and reduced life expectancy, all of which may be tied to climatic variation. A trend of decreasing female mean size toward the northernmost extent of the current introduced range of this species may be indicative of diminished impacts and invasive success. Geographical variation in morphology and its associated implications should be evaluated when considering the potential impacts of invasive species.

A systematic revision of the genus Archocentrus (Perciformes: Cichlidae), with the description of two new genera and six new species

The cichlid genus Archocentrus has been considered one of the most promising (i.e., possibly natural) genera resurrected to receive some of the species formerly included in Cichlasoma. Evidence is presented to justify generic recognition of Archocentrus, as well as eight other closely related genera (Caquetaia, Hypsophrys, Parachromis, Amphilophus, Archocentrus, Cryptoheros, Amatitlania, and Rocio). Of these, Amatitlania (type species, A. nigrofasciata) and Rocio (type species, R. octofasciata) are described as new. The present revision treats all nominal species ever assigned to Archocentrus, as well as species that have been included in or near the same clade as Archocentrus centrarchus (type species of the genus) in available phylogenetic analyses. Geographical variation in morphology of the more widespread species was examined, which has resulted in the description of six new species (Cryptoheros chetumalensis, Amatitlania coatepeque, A. kanna, A. siquia, Rocio gemmata, and R. ocotal) with a seventh resurrected from synonymy (Cryptoheros cutteri). Archocentrus includes the type species (Ar. centrarchus), plus Ar. spinosissimus and Ar. multispinosus. Cryptoheros is restricted to the species complexes of Cr. spilurus (= subgenus Cryptoheros, including also Cr. chetumalensis and Cr. cutteri) and Cr. septemfasciatus (= Bussingius n. subgen., including also Cryptoheros altoflavus, Cr. nanoluteus, Cr. myrnae, and Cr. sajica); Cryptoheros panamensis is placed in Panamius n. subgen. Herotilapia is synonymized with Archocentrus, and Neetroplus is synonymized with Hypsophrys, which now includes the type species H. nicaraguensis and H. nematopus. Lectotypes are designated for Amatitlania nigrofasciata, Archocentrus spinosissimus, Cryptoheros septemfasciatus, Cr. spilurus, and Rocio octofasciata. Cichlasoma immaculatum is considered to be a synonym of Archocentrus spilurus, not of Ar. spinosissimus.

Morphological variation in Sarracenia purpurea (Sarraceniaceae): geographic, environmental, and taxonomic correlates

Geographic variation in morphology reflects phenotypic responses to environmental gradients and evolutionary history of populations and species and may indicate local or regional changes in environmental conditions. The pitcher plant (Sarracenia purpurea) illustrates these principles. At local scales, its morphology reflects nutrient availability. At points along its broad geographic range (from Florida to northern Canada) morphology has been used to distinguish subspecies and varieties, but there has been no detailed study of the continuum of morphological variation across this entire range. Patterns of morphological variation in S. purpurea were characterized as a function of climatic and environmental conditions at 39 sites spanning its range. Differences in pitcher size and shape were strongly correlated with temperature, annual precipitation, and availability of ammonium and calcium in peat pore water. Pitcher shape (lip width, mouth diameter, and pitcher width) in Florida panhandle populations differed significantly from pitcher shape of all other populations, even after accounting for environmental correlations. In contrast, the northern and southern subspecies of S. purpurea (the latter exclusive of the Florida panhandle populations) cannot be distinguished based on these morphological measurements alone. These results support a recent proposal that identifies the Florida populations as a distinct species, Sarracenia rosea.

Behavioral differences among rainbow trout clonal lines.

Salmonid fish show considerable geographical variation in morphology, physiology, and behavior. Understanding the genetic mechanisms underlying this variation could be useful for enhancing aquaculture stocks, identifying unique populations for conservation, and determining the genetic factors underlying natural adaptation and domestication. As a first step toward the genetic dissection of salmonid behavioral diversity, we examined variation in behavior patterns among four clonal lines of rainbow trout ( Oncorhynchus mykiss ) derived from geographically diverse source populations with different domestication histories. Clonal lines were crossed with two outbred (i.e., not homozygous) females, and the resulting progenies were reared and tested under identical conditions. Clonal line had significant genetic effects on mean swim level, hiding, foraging, startle response, and aggression level. Multiple comparisons suggest that domestication history of the source populations had a strong influence on these behavior patterns. Progeny of two clonal lines derived from populations reared in captivity for over 100 years exhibited reductions in predator avoidance behavior patterns and increases in aggression compared to progeny of two clonal lines from more recently domesticated populations. These results will facilitate future investigation of the genetic factors underlying population variation in these behavior patterns influenced by domestication.

Geographic variation in morphology and flavonoid chemistry in Hebe pubescens and H. bollonsii (Scrophulariaceae), including a new infraspecific classification for H. pubescens

Geographic variation in morphology, leaf anatomy, and flavonoid chemistry is appraised in Hebe pubescens, H. bollonsii, and allied plants from islands of outer Hauraki Gulf, North Island, New Zealand. The circumscription of H. pubescens is modified to include plants from Great Barrier, Little Barrier, and the Mokohinau Islands, as well as the Coromandel Peninsula and immediately surrounding islands. A new infraspecific classification is proposed for H. pubescens, wherein three subspecies are recognised. Subspecies pubescens occurs on the Coromandel Peninsula and immediately surrounding islands, and also at Papanui Point on the western coast of the Firth of Thames. Subspecies rehuarum occurs on Great Barrier Island. Subspecies sejuncta occurs primarily on the Mokohinau Islands and Little Barrier Island, with a single plant also known on Great Barrier Island. Populations of H. pubescens probably form a cline of variation, and some forms of subsp. sejuncta share morphological features with H. bollonsii, which is here considered restricted to the Poor Knights Islands, the Hen and Chickens Islands, and nearby areas of the Northland coast. Possible relationships of H. pubescens and H. bollonsii are discussed. A key to the taxa of Hebe pubescens is provided.

Dispersal, Mimicry, and Geographic Variations in Northern Melanesian Birds

I present new information about 34 of the 195 resident land and freshwater bird species of Northern Melanesia, an area characterized by a rich avifauna, high endemism, and great geographic variation in morphology. There are many examples of geographic variation in voice, behavior, habitat preference, altitudinal range, vertical stratum, abundance, and nest. Possible vocal convergence or mimicry between sympatric populations of different species is described between the goshawk Accipiter albogularis and the kingfisher Halcyon chloris, between the cuckoo-shrike Coracina [tenuirostris] and other species in its mixed-species foraging flocks, between the white-eyes Zosterops murphyi and Z. rendovae kulambangrae, and between the starlings Aplonis grandis and Mino dumontii. Hybridization is reported between the Bismarck and New Guinea races of the cuckoo Eudynamys scolopacea on Long Island (described as a new subspecies), between the whistlers Pachycephala pectoralis and P. melanura, and between the honey-eaters Myzomela tristrami and M. cardinalis. Cyclones bring Australian species, some of which occasionally remain to breed. Over-water dispersal ability varies greatly, from species that can be seen flying over water any day to species that rarely or never cross water. For instance, a channel 12 km long and only 0.15-1 km wide divides Florida Island into two halves, one of which possesses and the other of which lacks a resident population of the coucal Centropus milo.

Patterns of Morphological Variation in <I>Speyeria idalia</I> (Lepidoptera: Nymphalidae) with Implications for Taxonomy and Conservation

Patterns of intraspecific variation in the size of ventral wing spots were examined among populations of Speyeria idalia Drury. All morphological variables were significantly correlated with longitude but not latitude. Principal components and discriminant function analyses of the morphological data were also consistent with a longitudinal, clinal pattern of variation. Geographic variation in morphology was concordant with patterns of mitochondrial DNA, which showed fixed differences between eastern and western populations. Inclusion of samples from populations that are currently extinct in the center of the species' range suggests clinal, rather than the currently observed discrete, variation was originally present. The appearance of discrete variation due to extinction in the center of a cline has previously been observed in the tiger beetle Cicindela dorsalis Say and may be more common than has previously been acknowledged. These results lend support the idea that conservation should attempt to preserve historical patterns of intraspecific variation rather than protect a limited number of individuals in a given species.

Geographic morphological variation of siscowet lake trout in Lake Superior based on whole-body morphometries

Geographic morphological variation of siscowet lake trout in Lake Superior based on whole-body morphometries

Phylogeography and natural selection in the Tenerife gecko Tarentola delalandii: testing historical and adaptive hypotheses.

Combining phylogeographic and matrix correspondence approaches in the analysis of geographical variation provides a fruitful approach to inferring the causes of molecular and morphological evolution within species. Here we present a study on the gecko Tarentola delalandii on the island of Tenerife, Canary Islands, which provides an outstanding model of an exceptionally high degree of phylogeographic differentiation in magnitude and pattern on a small spatial scale. We reconstruct the population history of T. delalandii using phylogeographic information, matrix correspondence tests and estimates of divergence times in conjunction with geological data. It appears that populations differentiated on three precursor islands and secondary contact followed the junction of these islands. The cytochrome b sequence appears to be evolving at least at approximately 1% per million years in this species. Matrix correspondence tests indicate that morphological character systems may reflect ecological selection regimes (colour pattern), history (body dimensions) or both (scalation). The results imply that natural selection can override a historical legacy, but also underline the potential relevance of molecular phylogenetic data for the interpretation of geographical variation in morphology.

MORPHOLOGICAL VARIATION AMONG MIGRATORY AND NON-MIGRATORY POPULATIONS OF PRAIRIE WARBLERS

The two subspecies of Prairie Warblers (Dendroica discolor) differ in migratory behavior and habitat use. A concurrent study of mitochondrial DNA variation showed that behavioral differences between subspecies may persist because little gene flow occurs between subspecies. To determine whether geographic variation in morphology parallels variation in migratory behavior and mitochondrial DNA, I used measurements of museum specimens from throughout the Prairie Warbler's range. The subspecies differ in overall body size, with birds of the Florida subspecies (D. d. paludicola) significantly larger than the nominate race. Males of the subspecies differ in the extent of white coloration in the outer rectrices. These differences were apparent even among specimens collected in northern Florida and southern Georgia, where the subspecies' ranges are most proximate. Morphological differences coincide with differences in behavior and mitochondrial DNA and support the recognition of migratory and non-migratory forms of Prairie Warblers as subspecies and as potentially independent evolutionary lineages.

Phylogeography of skinks (Chalcides) in the Canary Islands inferred from mitochondrial DNA sequences.

Mitochondrial DNA (mtDNA) evolution was investigated in skinks of the genus Chalcides found in the Canary Islands (Ch. sexlineatus, Ch. viridanus and Ch. simonyi), together with some North African congenerics (Ch. polylepis and Ch. mionecton). Several sites were included within islands to cover areas of known within-island geographical variation in morphology. Skinks from the islands of El Hierro and La Gomera appear to be sister taxa. The relationships between this clade and the Tenerife and Gran Canarian skinks were not fully resolved, although the best working hypothesis indicated monophyly with the former, with the latter forming a closely related outgroup. Ch. simonyi from Fuerteventura was more distantly related to the Western Canary Island skinks and did not show close relationships with the North African species Ch. mionecton and Ch. polylepis. Possible colonization sequences for the four most Western Canary Islands were considered. El Hierro appears to have been colonized relatively recently from La Gomera, commensurate with the recent origin of this island, while dispersal between La Gomera and Tenerife and between Gran Canaria and Tenerife or La Gomera appears to have taken place considerably earlier. Substantial within-island haplotype divergence was found in Gran Canaria and Tenerife. This may be a result of recent periods of intense volcanic activity found within these two islands. Lower levels of within-island differentiation are found in La Gomera and El Hierro and may be explained by lower levels of volcanic activity during recent geological history and a more recent colonization, respectively.

Geographic variation in lizard phenotypes: importance of the incubation environment

Geographic variation in phenotypes can result from proximate environmental effects as well as from underlying genetic factors. Reciprocal transplant experiments, in which organisms are moved from one area to another, offer a powerful technique to partition the effects of these two factors. However, many studies that have utilized this technique have focused on the post-hatching organism only and ignored potential effects of environmental influences acting during embryonic development. We examined the phenotypic responses of hatchling scincid lizards (Lampropholis guichenoti) incubated in the laboratory under thermal regimes characteristic of natural nests in two study areas in southeastern Australia. Although the sites were less than 120 km apart, lizards from these two areas differed in thermal regimes of natural nests, and in hatchling phenotypes (morphology, locomotor performance). We incubated eggs from each area under the thermal regimes typical of both sites. Some of the traits we measured (e.g. hatchling mass and snout-vent length) showed little or no phenotypic plasticity in response to differences in incubation conditions, whereas other traits (e.g. incubation period, tail length, inter-limb length, body shape, locomotor performance) were strongly influenced by the thermal regime experienced by the embryo. Thus, a significant proportion of the geographic variation in morphology and locomotor performance of hatchling lizards may be directly induced by differences in nest temperatures rather than by genetic divergence. We suggest that future studies using the reciprocal transplant design should consider environmental influences on all stages of the life-history, including embryonic development as well as post-hatching life.

Geographic variation in lizard phenotypes: importance of the incubation environment

Geographic variation in phenotypes can result from proximate environmental eVects as well as from underlying genetic factors. Reciprocal transplant experiments, in which organisms are moved from one area to another, oVer a powerful technique to partition the eVects of these two factors. However, many studies that have utilized this technique have focused on the post-hatching organism only and ignored potential eVects of environmental influences acting during embryonic development. We examined the phenotypic responses of hatchling scincid lizards (Lampropholis guichenoti) incubated in the laboratory under thermal regimes characteristic of natural nests in two study areas in southeastern Australia. Although the sites were less than 120 km apart, lizards from these two areas diVered in thermal regimes of natural nests, and in hatchling phenotypes (morphology, locomotor performance). We incubated eggs from each area under the thermal regimes typical of both sites. Some of the traits we measured (e.g. hatchling mass and snout-vent length) showed little or no phenotypic plasticity in response to diVerences in incubation conditions, whereas other traits (e.g. incubation period, tail length, inter-limb length, body shape, locomotor performance) were strongly influenced by the thermal regime experienced by the embryo. Thus, a significant proportion of the geographic variation in morphology and locomotor performance of hatchling lizards may be directly induced by diVerences in nest temperatures rather than by genetic divergence. We suggest that future studies using the reciprocal transplant design should consider environmental influences on all stages of the life-history, including embryonic development as well as post-hatching life.

A genetic basis for geographic variation in shell morphology in the bay scallop, Argopecten irradians

The bay scallop, Argopecten irradians, exhibits extensive variation in morphology among geographically separated populations, resulting in the recognition of three major subspecies (A. i. irradians, A. i. concentricus, A. i. amplicostatus). The extent to which morphological variation results from differing environmental conditions is unknown. In the present study, bay scallops from Massachusetts, North Carolina, Florida, and Texas were collected, spawned and the offspring reared in a common garden experiment to determine if scallops cultured under similar environmental conditions exhibited the morphology expected given the geographic origin of their parents. Significant differences among populations were indicated by ANOVA in both the wild-caught (13/14 morphological characters) and cultured (11/14 characters) scallops. Principal components analysis clustered wild-caught scallops according to geographic origin and cultured scallops according to geographic ancestry. The morphological characters most influential in resolving groups were plical width, plical spacing, number of plicae and valve convexity. Geographic variation in morphology apparently has a strong genetic basis, and reflects significant differentiation among disjunct populations of bay scallops.

Distinguishing between primary and secondary intergradation among morphologically differentiated populations of Anolis marmoratus

Distinguishing between primary and secondary intergradation among differentiated populations, and the relative importance of drift and selection, are persistent problems in evolutionary biology. An historical perspective on population interactions can provide insight into the nature of contacts, and thus help resolve these questions. Continuously distributed populations of Anolis marmoratus from the island of Basse Terre in the Guadeloupean archipelago of the Lesser Antilles show a striking degree of geographic variation in morphology. Initial surveys of mtDNA variation from throughout the Guadeloupean Archipelago revealed one case where levels of sequence difference and phylogenetic relationships of alleles from morphologically differentiated populations from the east coast of Basse Terre were consistent with primary intergradation. In this paper, I examine the genetic population structure of a series of populations spanning this north-south cline in morphological variation to test the hypothesis of primary intergradation. Sequences of the mitochondrial cytochrome-b gene from 50 individuals representing five populations spanning the cline were obtained and fourteen unique haplotypes (differing by 2% or less) were detected. Patterns of nucleotide substitution among haplotypes do not deviate from neutral expectation indicating no effect of selection at the level of mtDNA sequences. Estimates of population structure and gene flow were made using both summary statistics for nucleotide diversity (Nst) and cladistic methods. The results are sensitive to the choice of gene flow model, and this is discussed in detail. Mitochondrial variation in the northern populations may not be at equilibrium, and the phylogeny of alleles is consistent with a recent increase in effective population size. Estimates of nucleotide diversity, gene flow, and the phylogenetic relationships of haplotypes indicate that the southern-most population (representing the extreme of morphological variation along this cline) has been relatively isolated from populations to the north and has experienced a reduced effective population size. The apparent clinal variation between the southern population and the others may therefore reflect secondary contact and introgression rather than primary intergradation.

Comparative Methods at the Species Level: Geographic Variation in Morphology and Group Size in Grey-Crowned Babblers (Pomatostomus temporalis)

Comparative Methods at the Species Level: Geographic Variation in Morphology and Group Size in Grey-Crowned Babblers (Pomatostomus temporalis)

The microhabitat and morphology ofGrubea cochlearon the gills of mackerel from lyme bay, Southern England

The microhabitat and morphology ofGrubea cochlear(Monogenea), a rare gill parasite of Atlantic mackerel (Scomber scombrus), were investigated for a sample of fourteen parasite individuals obtained from Lyme Bay, southern England.Grubea cochlearshowed a preference for the inner hemibranch of the fourth gill arch, this localization contrasting with that of the related and sympatric speciesKuhnia scombri. The morphology ofG. cochlearin this sample differed slightly from some of the previously documented specimens, especially with regard to the number of small genital hooks and the relative size of the haptor. It is suggested that geographical morphological variation may occur in this species.

Geographic Variation in Morphology of Spikedace, Meda fulgida, in Arizona and New Mexico

Geographic Variation in Morphology of Spikedace, Meda fulgida, in Arizona and New Mexico

Geographic Variation in Morphology and Allozymes of South American Imperial Shags

To evaluate the hypothesis that Pleistocene glaciations in southern South America effected differentiation in the Imperial Shag (Phalacrocorax atriceps), I analyzed geographic variation in plumage, skeletal size and proportions, and allozymes in populations from seven South American localities. Alar bar size, crest length, and the size of the white dorsal patch vary geographically among juveniles but not adults, and the alar bar and white dorsal patch are both present all year in adults. Geographic variation in osteology is marked, with males showing more interpopulational differentiation than females. Coastal populations follow Bergmann's rule, while freshwater Fuegian lake shags are smaller than coastal populations even though the geographically nearest coastal population is the largest one in body size. Shags from the lowest latitude, in central Chile, have relatively long culmens, conforming to Allen's rule. All populations except that from Chubut Province are very similar in allozyme frequencies, and the very low genetic distances between populations are noncongruent with the greater degree of morphological differentiation, particularly between lake and coastal populations. The genetically differentiated Chubut population was probably somewhat isolated on the Patagonian Massif, a circumstance unrelated to Pleistocene glaciations. Chilean shags were probably not long reduced during glaciations to a small isolate, because they can form colonies on unglaciated headlands; they are only slightly differentiated from Atlantic populations. The treatment of the Falkland Islands population as a distinct subspecies is supported by plumage characters. The freshwater Fuegian shags must have differentiated since glacial recession. The populations from the southern Atlantic coast and coastal Tierra del Fuego, which were probably contiguous throughout the Pleistocene, differ from each other only clinally in size. Unlike the cases of other Fuego-Patagonian species studied, Pleistocene vicariance events appear to have had little influence on the evolutionary history of the Imperial Shag. This is probably related to life-history traits of this species such as coloniality, vagility, longevity, trophic generalism, and cold tolerance.