Genetic variation in the onychophoran Plicatoperipatus jamaicensis

Abstract

The Onychophora are a relic taxon which diverged early in the arthropod radiation and have shown little morphological differentiation for several hundred million years. Jamaica has the richest onychophoran fauna in the Caribbean and although only five species are known, they represent 7 per cent of the global fauna. The present study involved an analysis of allozyme and mtDNA diversity in Plicatoperipatus jamaicensis, an endemic species which is the commonest onychophoran on the island. The work showed that P. jamaicensis includes at least two different species. These taxa are largely allopatric, but co-occur at some sites without interbreeding. Allozyme and mtDNA analyses suggest their divergence in the early Pleistocene, following the Pliocene origin of the Plicatoperipatus lineage from a Macroperipatus ancestor. Allozyme variation in both species was unusually low, but sufficient to confirm that each taxon reproduces sexually. Mitochondrial DNA diversity was abundant in both species and indicated that local aggregations did not consist of kin groups. The mitochondrial genomes of both species were small enough to suggest that their organizations are unusual.

Molecular diversity of Dunedin peripatus (Onychophora: Peripatopsidae)

“…The fact that genetic and geographic distances within group A are not correlated also suggest absence of gene flow. With the exclusion of the Piano Flat peripatus, groups A and B have withingroup genetic distances similar to one another, and similar to a study of Jamaican peripatus which found mtDNA distances between presumed sister species of 3.3% (Hebert et al 1991). In the Jamaican example, species status was evident from the lack of gene flow encountered between sympatric peripatus using allozymes.…”

“…In a sense this is a reversal of the situation that arises from morphology-based analyses which, naturally, tend to underestimate biogenetic diversity (Avise 1994). In the study of Onychophora for instance, a group noted for their morphological conservatism, genetic methods have revealed extensive cryptic diversity , stimulated revision of morphology based taxonomy (Reid 1996) and provided insights into the origin of diversity within, and biogeography of, species (Hebert et al 1991;Gleeson et al 1998).…”

“…It is of no surprise therefore that early morphology-based taxonomy also tended to be conservative and to underestimate the true diversity of the group. Molecular studies and the use of electron microscopy have revealed the existence of many cryptic species and genera, most notably in Australia Reid 1996) although the first genetic study was on Jamaican peripatus (Hebert et al 1991). The Australian onychophoran fauna appears to be both diverse, including some 80% of the described global fauna Reid 1996), and locally rich with some areas having as many as five genera (Sunnucks et al in press).…”

Phylogenetic Relationships among Onychophora from Australasia Inferred from the Mitochondrial Cytochrome Oxidase Subunit I Gene

“…Finally, the possibility of onychophoran migration across large expanses of oceans has been discussed and discounted previously (Poinar, 1996); however, there is good evidence for dispersal over comparatively shorter distances in the Carribean (Hebert et al, 1991;Monge-Najera, 1995). Hence if our phylogenetic reconstructions are to be taken at face value, and given current theories on vicariance patterns, this last possibility requires further investigation.…”

Sympatric cryptic species in New Zealand Onychophora

“…The traditions of taxonomy, set as they are in morphology, have tended to underestimate actual biological diversity in many groups and the use of molecular techniques has led to the discovery of numerous discrete genetic groupings within recognized species boundaries (Hebert et al, 1990;Eldridge & Close, 1992;Briscoe & Tait 1995). An empirical framework for the identification of species therefore exists, within which corollaries of subtle morphology and perhaps more importantly ecology can be explored (Mayr, 1942).…”