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Home    Η διαφοροποίηση του γένους mastus (gastropoda, pulmonata, buliminidae) στον ελλαδικό χώρο. Μια συγκριτική μελέτη με μεθόδους οικολογίας, μορφομετρίας και μοριακής ανάλυσης  

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Identifier uch.biology.phd//2003parmakelis
Title Η διαφοροποίηση του γένους mastus (gastropoda, pulmonata, buliminidae) στον ελλαδικό χώρο. Μια συγκριτική μελέτη με μεθόδους οικολογίας, μορφομετρίας και μοριακής ανάλυσης
Alternative Title The differentiation of the genus mastus (gastropoda, pulmonata, buliminidae) in the hellenic region. A comparative approach with methods of ecology, morphometry and molecular analyses
Author Παρμακέλης, Αριστείδης
Thesis advisor Μυλωνάς, Μωυσής
Abstract The genus Mastus is one of the land snail genera distributed in the Aegean Archipelago that exhibits extremely high morphological (shell and terminal genitalia) diversity contrary to the uniformity it presents in the rest of its distribution area. This high degree of diversity is very puzzling for scientists and is rather confusing in determining the actual number of species present in the area. On the other hand, the morphological plasticity of the genus has a very important interest in its own right. Questions regarding the evolutionary processes acting in favour of the high diversity or the validity of certain morphological characters in the taxonomy of the genus, derive from the high levels of divergence observed in the genus. These kind of questions are being addressed within the present study. At this point we have to note that this is the first time that a molecular phylogeny of the genus is implemented. Thus, an another important issue regards whether the observed morphological diversity of the genus in the Aegean Archipelago, is accompanied by equivalent levels of genetic diversity. The answer to the latter question is of major importance for the investigation of the phylogeny of the genus. At the same time, within the frame of the elucidation of the taxonomy of the genus, an evaluation of the morphological characters that have been used up to now, is taking place in the light of the molecular data. Additionally, issues such as what is the involvement of natural selection in the formation of Mastus diversity or do natural processes such as isolation by distance and natural selection or historical processes, have the same effect upon the different levels of diversity (morphological, genetic), in both space and time? The results of a classical and a more elaborate approach, are combined together and the resulting grouping of populations is contrasted to the palaeogeography of the region, in an effort to formulate the biogeographic scenarios that have defined the present day distributions of Mastus species. Additionally, a molecular phylogeny derived from the use of the mtDNA and nuclear markers, is exploited in order to infer the differentiation and speciation pattern of the genus. In the course of achieving the aims of the study, in the 3rd Chapter, 51 populations (23 species) are submitted to multivariate analyses of their shell characteristics (quantitative continuous characters). Out of the 51 populations 39 of them are from Crete and its surrounding island groups, 2 are from the island of Skyros, 2 from the island of Antikythira and 1 from each of the following islands: Evvoia, Paros, Syros, Karpathos, Lesvos, Samos, Ikaria and Sicily. Most of the species were represented in the study with one or more populations and in order to avoid species misidentifications one of the populations was from the type locality of the species. The shell variables measured were 16 and the number of shells was 1,060. The multivariate analyses performed were Principal Component Analysis, Discriminant Analysis and Hierarchical Clustering. A major conclusion of the multivariate analyses was that the phylogenetic importance of the shell is diminished by the high levels of homoplasy and the geographical pattern of differentiation that the shell variables exhibit. Consequently, the use of shell characters in the phylogeny of the genus, will most probably result in dubious populations groupings not reflecting the true relationships of the taxa involved. In the 4th Chapter the phylogeny is inferred with the use of mtDNA and nuclear markers. The populations studied were the same with those referred to in Chapter 3. The molecular markers used were the 16S rRNA gene and the nuclear ribosomal markers 5.8S, ITS2 and 28S rRNA. In total 121 mtDNA sequences and 46 nuclear sequences were used. The phylogenetic techniques implemented were Neighbor Joining, Maximum Parsimony and Maximum Likelihood. In Chapter 4 it is concluded that the level of divergence exhibited by the mtDNA haplotypes is adequate for the resolution of the phylogeny of recently separated clades, while the nuclear haplotypes serve for the investigation of older separations. The phylogenetic trees obtained from the molecular data, were in congruence with the palaeogeography of the region, and allowed the speculation that the genus differentiates in the Aegean Archipelago at least since Miocene. At the same time, the phylogenetic trees were in favour of the importance of the terminal genitalia and the spermatophore morphology in the taxonomy of the genus. Additionally, the island groups participating in the study indicated that the effects of insularity, on the genetic and morphological differentiation of island populations, is not predefined. It was very impressively shown that the formation of the genetic and morphological differentiation of island populations is ruled by factors such as the abiotic elements of the islands, the among island group relationships (separation times of islets e.t.c.), the biology and ecology of the studied species as well as the human activities taking place in the island group. Finally, in Chapter 2 the population structure, the dispersal ability, the spatial distribution, the habitat preferences and the densities of two Mastus species are investigated. The study took place in an area 10Km east of the city of Irakleio (Crete), where the species M. butoti and M. cretensis occur in sympatry. The study lasted 3 years and both mark-recapture and random quadrat sampling were implemented. In total 456 individuals of M. butoti and 321 M. cretensis individuals were marked. According to the results of Chapter 2, both Mastus species have highly structured populations, exhibit very small dispersal trends, retain very small densities and have a small aggregation tendency in the field. Consequently, small demes within the limits of a population act as the panmictic units and processes such as isolation by distance play a major role in the formation of the genetic and morphological diversity of populations. However, the results of this chapter combined with those of Chapter 4, provide indications that certain life history traits of the species, might also be strongly related to the overall diversity of a population. Additionally, the three years observations have pointed out the tendency of both Mastus species to prefer certain habitats in the field. In both species, the habitats preferred during the active and the aestivation period were not the same. No competition between Mastus species studied was observed at any point of the study.
Language Greek
Issue date 2003-11-29
Date available 2004-01-16
Collection   School/Department--School of Sciences and Engineering--Department of Biology--Doctoral theses
  Type of Work--Doctoral theses
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