Limited Vagility Research Articles

Strength of Habitat and Landscape Metrics in Predicting Golden‐Headed Lion Tamarin Presence or Absence in Forest Patches in Southern Bahia, Brazil

ABSTRACTWe investigated the effects of forest fragmentation on golden‐headed lion tamarins (Leontopithecus chrysomelas) by qualitatively and quantitatively characterizing the landscape throughout the species range, conducting surveys, and exploring predictive models of presence and absence. We identified 784 forest patches that varied in size, shape, core area, habitat composition, elevation, and distance to neighboring patches and towns. We conducted 284 interviews with local residents and 133 playback experiments in 98 patches. Results indicated a reduction in the western portions of the former species range. We tested whether L. chrysomelas presence or absence was related to the aforementioned fragmentation indices using Monte Carlo logistic regression techniques. The analysis yielded a majority of iterations with a one‐term final model of which Core Area Index (percent of total area that is core) was the only significant type. Model concordance ranged between 65 and 90 percent. Area was highlighted for its potential predictive ability. Although final models for area lacked significance, their failure to reach significance was marginal and we discuss potential confounding factors weakening the term's predictive ability. We conclude that lower Core Area Index scores are useful indicators of forest patches at risk for not supporting L. chrysomelas. Taken together, our analyses of the landscape, survey results, and logistic regression modeling indicated that the L. chrysomelas metapopulation is facing substantial threat. The limited vagility of lion tamarins in nonforest matrix may lead to increasingly smaller and inbred populations subject to significant impact from edge effects and small population size. Local extinction is imminent in many forest patches in the L. chrysomelas range.

A heterogeneity test for fine‐scale genetic structure

For organisms with limited vagility and/or occupying patchy habitats, we often encounter nonrandom patterns of genetic affinity over relatively small spatial scales, labelled fine-scale genetic structure. Both the extent and decay rate of that pattern can be expected to depend on numerous interesting demographic, ecological, historical, and mating system factors, and it would be useful to be able to compare different situations. There is, however, no heterogeneity test currently available for fine-scale genetic structure that would provide us with any guidance on whether the differences we encounter are statistically credible. Here, we develop a general nonparametric heterogeneity test, elaborating on standard autocorrelation methods for pairs of individuals. We first develop a 'pooled within-population' correlogram, where the distance classes (lags) can be defined as functions of distance. Using that pooled correlogram as our null-hypothesis reference frame, we then develop a heterogeneity test of the autocorrelations among different populations, lag-by-lag. From these single-lag tests, we construct an analogous test of heterogeneity for multilag correlograms. We illustrate with a pair of biological examples, one involving the Australian bush rat, the other involving toadshade trillium. The Australian bush rat has limited vagility, and sometimes occupies patchy habitat. We show that the autocorrelation pattern diverges somewhat between continuous and patchy habitat types. For toadshade trillium, clonal replication in Piedmont populations substantially increases autocorrelation for short lags, but clonal replication is less pronounced in mountain populations. Removal of clonal replicates reduces the autocorrelation for short lags and reverses the sign of the difference between mountain and Piedmont correlograms.

Pattern and process in the ecological biogeography of European freshwater fish

1. Species lists for regions of Europe defined by Illies (1978, Limnofauna Europaea, 2nd edn. Gustav Fischer Verlag, Stuttgart), and augmented by information from Maitland (2000, Guide to Freshwater Fish of Britain and Europe. Hamlyn, London), are used to describe patterns in freshwater fish species richness and to examine the contribution of habitat preference, migration, body size and glacial history to these patterns. 2. The number of non-endemic species declines to the north and west, with increasing distance from the Ponto-Caspian region, the main source area, whereas endemic species richness declines only with latitude. 3. Habitat generalists tend to be migratory while riverine specialists are usually resident. Similar numbers of riverine species and generalists occur in Europe as a whole but generalists dominate in regional faunas and, to an increasing extent, in more isolated, formerly glaciated areas. Very few lacustrine specialists were found, reflecting the geologically ephemeral nature of lakes. Only 8% of riverine species have colonized glaciated areas, compared with more than half the generalist species, and the number declines rapidly with increasing distance from the source area. 4. Diadromous species show no geographical variation in species richness but potamodromous and resident species are affected by glaciation and by mountain and marine barriers. 5. The mean body size of regional faunas increases with latitude because there are relatively fewer small species in more distant, glaciated areas. 6. About half the species occurring in Europe are restricted to one region and the majority of these endemics occur in barrier regions with Mediterranean climates. Species in glaciated regions have much larger range sizes. Habitat preference and migration type, not body size, are the main determinants of range size. 7. Freshwater habitat availability varies across Europe with glaciated areas having more lakes of a given size than unglaciated areas. Catchment size is greatest at mid-latitudes. For a given catchment size rivers in glaciated areas are shorter. 8. The results support the notion that habitat variability, on both short and long time scales, favours colonization ability, which requires large body size. 9. As a result of their limited vagility northern fish faunas are depauperate, show high levels of plasticity and polymorphism and may show elevated speciation rates. The isolated southern faunas of the Iberian and Italian peninsulas and the Balkans are rich in endemic species but may be subject to extinctions because of the spread of the highly seasonal Mediterranean climate.

The trans‐Pacific zipper effect: disjunct sister taxa and matching geological outlines that link the Pacific margins

AbstractAim To combine analyses of trans‐Pacific sister taxa with geological evidence in order to test the hypothesis of the existence of a Panthalassa superocean.Location The study is concerned with taxa, both fossil and extant, from East Asia, Australia, New Zealand, South America and North America.Methods Phylogenetic and distributional analyses of trans‐Pacific biota were integrated with geological evidence from the Pacific and circum‐Pacific regions.Results A series of recent biogeographical analyses delineates a zipper‐like system of sister areas running up both margins of the Pacific, with each section of western North and South America corresponding to a particular section from East Asia/Australia/New Zealand. These sister areas coincide neatly with a jigsaw‐like fit provided by the matching Mesozoic coastlines that bracket the Pacific.Main conclusions The young age (<200 Myr) of oceanic crust, the matching Mesozoic circum‐Pacific outlines, and a corresponding system of interlocking biogeographical sister areas provide three independent avenues of support for a closed Pacific in the Upper Triassic–Lower Jurassic. The hypothesis of the existence and subsequent subduction of the pre‐Pacific superocean Panthalassa is not only unnecessary, it conflicts with this evidence. Panthalassa‐based paleomaps necessitate the invention of dozens of additional hypotheses of species‐dependent, trans‐oceanic dispersal events, often involving narrow‐range taxa of notoriously limited vagility, in order to explain repeated examples of the same biogeographical pattern. Removing the vanished‐superocean hypothesis reunites both the matching geological outlines and all the disjunct sister taxa. In brief, what appears to be a multi‐era tangle of convoluted, trans‐oceanic distributions on Panthalassa‐based paleomaps is actually a relatively simple biogeographical pattern that is explainable by a single vicariant event: the opening and expansion of the Pacific.

Hierarchical analysis of genetic structure in native fire ant populations: results from three classes of molecular markers.

We describe genetic structure at various scales in native populations of the fire ant Solenopsis invicta using two classes of nuclear markers, allozymes and microsatellites, and markers of the mitochondrial genome. Strong structure was found at the nest level in both the monogyne (single queen) and polygyne (multiple queen) social forms using allozymes. Weak but significant microgeographic structure was detected above the nest level in polygyne populations but not in monogyne populations using both classes of nuclear markers. Pronounced mitochondrial DNA (mtDNA) differentiation was evident also at this level in the polygyne form only. These microgeographic patterns are expected because polygyny in ants is associated with restricted local gene flow due mainly to limited vagility of queens. Weak but significant nuclear differentiation was detected between sympatric social forms, and strong mtDNA differentiation also was found at this level. Thus, queens of each form seem unable to establish themselves in nests of the alternate type, and some degree of assortative mating by form may exist as well. Strong differentiation was found between the two study regions using all three sets of markers. Phylogeographic analyses of the mtDNA suggest that recent limitations on gene flow rather than longstanding barriers to dispersal are responsible for this large-scale structure.

Innate landward orientation in the littoral isopod Tylos europaeus

Solar orientation experiments have shown that laboratory-born (inexpert) young of the littoral isopod Tylos europaeus are capable of using the sun compass to assume an escape direction corresponding to the Y axis of their mother's home shore. As in sandhoppers, the escape direction and capacity for solar orientation appear to be innate. The hypothesis whereby the direction of the sealand axis is innate in littoral arthropods with direct development, inhabiting rectilinear coastlines and having a limited vagility along the X axis is discussed.

Biogeographical aspects of Somalian orthopteran fauna

EIOGEOGFIAPHIA - vol. X/V — 1988 (Pubb/icato il 31 dicembre 1990) The Biogeography of Somalia Biogeographical aspects of Somalian orthopteran fauna BACCIO BACCETTI I7zsz‘.z'/fz/te of General! Biology, UI2z'1Jer5z'ty and Center for the Study of Ger/722'/ml Cells, C.N.R., Siemz, Italy SUMMARY In this paper the Author gives an interpretation of the actual consistence and distribution of Somalian orthopteran fauna on the basis of the palaeogeographical history of the territory. Several taxa, systematically well defined and having proved limited vagility, appear to have evolved according to important geological events. A biogeographical evaluation of the Orthopteran fauna of the Somali re- gion has never been attempted. Because the great number of new entities or new interpretations published every year as a result of more intensive studies on this subject by several specialists all around the world, the matter is very uncertain, and conclusions very doubtful. Nevertheless, on the occasion of a congress devoted to the biogeographical history of Somalia it is important to include Orthopterans. I will try, therefore, to suggest some conclusions, by selecting taxa systematically well defined and with limited vagility. It is commonly believed that the ancestor of Orthopterans must have been part of the Gondwanian fauna after the Cambrian period. Gondwana was an isolated entity, as were Angara, Cathays, and Euramerica (Cox, 1974), up to the Permian period (Fig. 1). The present distribution of many groups, like Eumastacoidea (Fig. 2) (Descamps, 1973), Pyrgomorphidae (Kevan, 1977), Phaneropteridae (Ragge, 1956) clearly indicate a precise Gondwanian original distribution. Spectacular exemples from the Somalian fauna are the Phaneropterid genus Dz/cetzkz (Fig. 3), still present in the tropical Africa, southern Asia, Indonesia, Japan, New Guinea, Solomon Isll, Australia (Ragge, 1961) and the subfamily Phlaeobinae, still distributed in the Ethio- pian, Malagassian, Oriental, Austro—oriental and Australian Region (Dirsh, 1975). The specific fragmentation is, as we will see, much recent, as a result of territorial fragmentation. In the upper Permian and Trias, Gondwana and Laurasia fused (Fig. 4) forming the Pangea (Cox, 1974). In this period, encompassing more than 100 million year, the great migrations of all principal orthopteran lines occurred. The asian triassic fossil ensiferan superfamily Hagloidea described by Go- 163

Taxonomic Congruence and Disparity in an Insular Ant Fauna: Rhytidoponera in New Caledonia

-Patterns of taxonomic congruence were examined in 17 of Rhytidoponera endemic to New Caledonia, using disparate data sets based on allozymes and morphology. These ants belong to four informal species groups, one of which is monotypic. Both phenetic (UPGMA clustering) and cladistic (minimum-length tree estimation) methods were employed. Adams-2 and strict consensus trees were constructed for all pairs of equivalent rival trees. Since the rival trees were fully resolved or nearly so, the degree of resolution of the consensus trees was used to assess the amount of taxonomic congruence and was measured with the consensus indices of Colless (1980; CIc) and Rohlf (1982:138; CIR). In addition, the confidence limits of the minimum-length tree based on the composite (allozymes + morphology) data set were estimated by 20 trial samplings of the data set, using a bootstrap method proposed by Felsenstein (1985). The rival data sets both produced single phenograms. Several topologically distinct minimumlength trees (cladograms) were found for both data sets. Both phenetic and cladistic methods gave poorly resolved consensus trees (CIC = 0.27, CIR = 0.24 for the strict consensus phenogram; CIc = 0.20 to 0.33, CIR = 0.07 to 0.26, for strict consensus cladograms). In the strict consensus trees, the species were generally preserved, but species-level relationships were not. The Adams-2 consensus trees were similar but also contained some resolved clusters of within the largest group. Bootstrapped confidence limits of the minimum-length tree derived from the composite data set were very broad, indicating that only a few tree partitions (subsets) were statistically significant. These subsets generally corresponded to the species groups. Based on limited conclusions about relationships among the New Caledonian Rhytidoponera (probable monophyly of the three major groups and of the group as a whole relative to extant congeners in Australia and New Guinea) and on the observation of limited vagility due to the absence of winged queens, I argue that these represent an archaic element in the ant fauna of New Caledonia, dating back to the early Tertiary. Poor resolution of relationships in the specialized and speciose pulchella group may reflect multiple, contemporaneous differentiation of taxa. [Taxonomic congruence; bootstrap; ant phylogeny; Rhytidoponera; New Caledonia.] The concept of taxonomic congruence has come to denote the degree of agreement between different classifications of the same group of organisms (Mickevich, 1978, 1980). When the rival classifications are based on different data sets analyzed by the same taxonomic method, taxonomic congruence provides a measure of the extent to which that method returns similar results in the face of shifting character sets. The character sets may be randomly chosen subsets or nonrandom partitions of the data base. There has been considerable controversy over the relative performance of cladistic and phenetic methods in such tests of taxonomic congruence (Mickevich, 1978, 1980; Rohlf and Sokal, 1980; Schuh and Polhemus, 1980; Schuh and Farris, 1981; Sokal and Rohlf, 1981; Rohlf et al., 1983; Sokal et al., 1984). In the present study, I examine patterns of taxonomic congruence in a group of closely related ponerine ants which have undergone a modest radiation on the island of New Caledonia (Kanaky). In effect, these ants provide the opportunity to test the relative robustness of different taxonomic procedures when applied to a compact but speciose group. The ant fauna of New Caledonia is notably disharmonic (i.e., taxonomically unbalanced) relative to the presumptive IndoAustralian source fauna (Emery, 1914; Ward, 1984). One of the genera that is disproportionately well represented on the island is Rhytidoponera, which accounts for 18 of the 152 ant (12%), compared with about 100 out of 3,000 (3%) in Australia (estimates derived from Brown, 1958; Ward, 1984; Ward, unpubl. data). The

REDUCTION OF GENE FLOW DUE TO THE PARTIAL STERILITY OF HETEROZYGOTES FOR A CHROMOSOME MUTATION. I. STUDIES ON A "NEUTRAL" GENE NOT LINKED TO THE CHROMOSOME MUTATION IN A TWO POPULATION MODEL.

The primary role of chromosome mutations that cause partial sterility of the heterozygote in triggering some processes of speciation is supported by an increasing amount of data. This type of speciation seems to have played a particularly important role in animal species with limited vagility. Among the more extensively studied examples are the Australian Morabinae (White, 1968, 1974), the complex Didymuria violescens (Bocquet, 1953; Lecher, 1964, 1967, 1968), the isopods Jaera (Lecher and Prunus, 1972) and the Mexican lizards of the complex Sceloporus grammicus (Hall and Selander, 1973). Besides these exemplary cases, there are numerous other situations of closely related species with different karyotypes in numerous groups of animals which have been interpreted in terms of chromosomal speciation mechanisms (see White, 1978a, 1978b, for a complete review). The mechanisms of chromosomal speciation are open to discussion. The stasipatric speciation model, proposed and developed by White (1968, 1978a, 1978b), envisages the production of a heterozygote mutant, the fixation of the mutation by genetic drift and the subsequent spread of the mutant homozygote population due to systematic factors advantageous to the mutation. Clarification and quantification of the processes and mechanisms involved with regard to sequence and hierarchy are necessary: besides further knowledge of individual examples, theoretical models are important to explain the onset, fixation (see Hedrick, 198 1), spread and accumulation of chromosome mutations and their role in reproductive isolation. We address here the efficiency, as a mechanism of reproductive isolation, of the partial sterility of heterozygotes for chromosome mutations. In this paper we quantify the efficiency of a single chromosome mutation that causes partial sterility of the heterozygote in reducing the gene flow. We use a model similar to the loci systems on which an extensive literature exists (see Hedrick et al., 1978), but which scarcely addresses the problem of chromosomal speciation. The model consists of two populations of the same size which come into contact and are initially monomorphic, one with a normal form and the other a mutated form of one specific chromosome. These populations differ in frequency for a pair of selectively neutral alleles, not linked to the chromosome involved in the mutation. We propose a model with non-overlapping generations based on the following parameters: 1) constant symmetrical migration rate between the two populations in the diploid stage (m); and 2) reduction of fitness, caused by the partial sterility of the heterozygote for the chromosome mutation (s). Our model will be based upon the following quantities: 1) the difference in frequency of the mutated chromosome in populations 1 and 2 at the nth generation (p ,n p2(n)); 2) the difference in frequen-

Natural Hybridization between Two Species of Collared Lizards (Crotaphytus)

Electrophoretic analysis of samples from contiguous populations of Crotaphytus collaris baileyi and C. insularis bicinctores provides conclusive evidence that the two taxa hybridize naturally. The hybrid zone at one locality is narrow (<1.7 km), suggesting strong selection against hybrids. Two genetic marker loci were examined and hybrids exhibited heterozygosity at one or both loci, or carried alleles of both species in the homozygous state. The morphological evidence and array of hybrid genotypes detected electrophoretically indicate that F, hybrids are sufficiently fertile to produce later generation and backcross hybrids. There is at present no conclusive evidence of a genetic and/or physiological basis for hybrid inferiority. Ecological and behavioral mechanisms potentially restricting hybridization include limited vagility imposed by habitat discontinuity, interspecific territorial aggression, and perhaps incipient sexual isolation. The taxonomic status of bicinctores is reviewed and its retention as a subspecies of C. insularis is recommended.

MECHANISMS OF FIXATION AND ACCUMULATION OF CENTRIC FUSIONS IN NATURAL POPULATIONS OF MUS MUSCULUS L. I. KARYOLOGICAL ANALYSIS OF A HYBRID ZONE BETWEEN TWO POPULATIONS IN THE CENTRAL APENNINES.

Chromosomal mutations causing partial sterility of the heterozygote are decisive in speciation processes in animals of limited vagility (e.g., Orthoptera and small mammals). In this regard the stasipatric speciation model (production of a heterozygous mutant, fixation in a small colony and subsequent spread of the homozygous mutant population) was proposed (see White, 1968, 1973, 1975, 1977), as opposed to the hypothesis of allopatric speciation (e.g., Key, 1974). Rodents offer several suitable characteristics for this type of study: 1) A variety of chromosomal rearrangements are involved: pericentric inversions, as in Spalax (Soldatovic and Savic, 1967; Wahrman et al., 1969; Lay and Nadler, 1972), Thomomys (Patton and Dingman, 1970), Perognathus (Patton, 1969), Peromyscus (Hsu and Arrighi, 1968) and, above all, centric fusions-and to a lesser extent, fissions-in Spalax (Wahrman et al., 1969; Lay and Nadler, 1972), Thomomys (Thaeler, 1968a; Nevo et al., 1974), Perognathus (Patton, 1969), Gerbillus (Wahrman and Gourevitz, 1973), Acomys (Wahrman and Goitein, 1972), Geomys (Selander et al., 1974) and Leggada (Matthey, 1970). 2) Different steps in the speciation process are evident: among different species of the same genus, among sibling species, among incipient species and among interbreeding populations. In Thomomys (Thaeler, 1968a, 1968b; Patton and Dingman, 1970;