Evidence For Long-distance Dispersal Research Articles

Speciation and biogeography of the Caloglossa leprieurii complex (Delesseriaceae, Rhodophyta).

Studies on the morphology, reproductive compatibility, life cycle and molecular phylogeny of the euryhaline red alga Caloglossa provide insights into the speciation events and biogeographic patterns. The C. leprieurii complex is separated into three morphotypes based on the number of cell rows at nodes and the blade width. The three morphotypes are reproductively incompatible with each other, and furthermore many mating groups are recognized within the morphotypes. Incomplete reproductive isolation is occasionally seen between geographically distant mating groups, whereas no sexual compatibility occurs between sympatrically or parapatrically distributed mating groups. In the molecular phylogenetic analyses, the C. leprieurii complex is resolved as two clusters that phenotypically correspond to the single and multiple cell row types, respectively. The strains belonging to the same mating group are closely related to each other, without exception, while the mating groups showing incomplete reproductive reactions do not always make a clade. The genetic distance is generally not correlative to the geographic distance, and this is also suggested by the morphological data and crossability. These results indicate that allopatric speciation has frequently occurred in this species complex, although there is some evidence of long-distance dispersal.

Molecular Phylogeny of Nepenthaceae Based on Cladistic Analysis of Plastid trnK Intron Sequence Data

Abstract: Nepenthaceae are an exceptional family with regard to carnivory and the uniformity of characters. This makes it difficult to resolve phylogenetic relationships due to convergent evolution of morphological features. Using comparative sequencing of the chloroplast trnK intron, the monophyly of this complex family and hypotheses of infrageneric relationships were tested. Sequences from 71 Nepenthes taxa, representing all groups and two taxa of the closely related Ancistrocladaceae and Dioncophyllaceae as outgroup, were determined and analysed using maximum parsimony methods. Results of this analysis show that the isolated taxa N. distillatoria (Sri Lanka) and N. pervillei (Seychelles) are the most basal, clearly separated from the Madagascan taxa N. madagascariensis and N. masoalensis which are placed in a distinct subclade. This corresponds with some plesiomorphic characters shared by these taxa. N. khasiana (North India) has an intermediate position between these relic Western species and the remaining taxa. The species of the Malay Archipelago can be referred to three distinct lineages which indicate a correlation to biogeography. Thus the recent disjunct distribution of Nepenthes is interpreted as a result of an incisive extinction of progenitors, a process of migration and a subsequent diversification on the islands of Borneo, Sumatra, Sulawesi and New Guinea.Based on our molecular data, two interpretations concerning the origin of Nepenthes are possible: i) evolution in the Northern Tethys which is supported by fossil pollen records from the European Focene, or, ii) a Gondwanaland origin at a time when the Indian plate was separated from Madagascar. Molecular data indicate that colonization of SE Asia started from an ancient Indian stock. Subsequently, in the Malay Archipelago a new secondary centre of diversity developed. Madagascar, the Seychelles and New Caledonia were probably reached by migration via land bridges, starting from widespead common ancestors with subsequent extinction leaving the current taxa. There is no evidence for long‐distance dispersal. Current infragenic classification of Nepenthes is only partly in accordance with the phylogeny inferred from trnK intron data.

Patterns of Elevational and Latitudinal Distribution, including a "Niche Switch," in Some Guans (Cracidae) of the Andes

A recently discovered population of Chamaepetes goudotii (Sickle-winged Guan) in the eastern Andes of southern Peru and northern Bolivia is anomalous in its high-elevation (above 3,000 m) distribution; populations from central Peru to not-them Colombia are found generally below 2,100 m. Several hypotheses are evaluated to account for the origin of such an unusual distribution. No evidence for long-distance dispersal or human introduction was found (and previous claims of introduction by ancient civilizations to account for disjunct distributions of two other species of New World birds are disputed). We propose that the current pattern is the result of fragmentation of a once continuous distribution. Hypotheses concerning the cause of the fragmentation and maintenance of the current pattern are evaluated. The relative consistency of elevational distributions of Andean bird species over broad latitudinal ranges (and dramatic differences in species composition with changes in elevation) provides circumstantial evidence against an autecological hypothesis that would propose that ecological requirements are met for C. goudotii only in the two disjunct regions. If potential competitors are restricted to congeners, no support can be found for a hypothesis based on interspecific competition. However, if the field of potential competitors is expanded to include morphologically similar confamilials, a striking pattern of generally nonoverlap- ping distributions in terms of elevation and latitude is revealed. Most striking is the reversal in elevations occupied by C. goudotii and Penelope montagnii. The reliance on interpretation for evaluating competing hypotheses makes such analyses inherently unsatisfying.

The possible significance of long-range dispersal for the biogeography of seaweeds

Indirect evidence of the existence of long-distance dispersal of seaweeds is provided by the fact that mid-oceanic islands of volcanic origin are inhabited by well-developed seaweed floras which could reach these islands only overseas from continental donor areas. For instance, the flora of Tristan da Cunha (S. Atlantic Ocean) was established by long-distance dispersal in less than 1 million years (the approximate age of the island); the seaweed flora of the Faeroes (N. Atlantic Ocean) could be constituted in less than 10,000 years (the end of the Pleistocene ice cover of these islands). There is no evidence for either supporting or discounting the possible role of planktonic stages of seaweeds (spores, propagules, zygotes) in the long-distance dispersal of seaweeds. There is, however, some evidence of long-distance dispersal as floating plants, or as plants attached to floating objects (including floating algae). There are a few examples of “artificial” long-range dispersal by man (possibly on ship hulls, oysters, in ballast water). Long-range dispersal of seaweeds does exist, but it is an exception rather than the rule. If it were the rule, the world’s seaweed floras would show similar latitudinal gradients in species composition in the oceans and on both hemispheres. This is, however, not the case.