Influencia de la interacción de los compuestos en la biodegradación de las mezclas de

Biogeographers have long debated the origins and evolutionary history of the biota of New Zealand and questioned whether its characteristic biota is the product of long isolation or if diversification and colonization postdate this event (Pole, 1994; McGlone, 2005; McDowall, 2008). Many molecular studies of the plants and animals of New Zealand have in recent years been carried out focussing on speciation and colonization of the biota of New Zealand (e.g. Gillespie & Roderick, 2002; Sanmartin & Ronquist, 2004; Cook & Crisp, 2005; Knapp et al., 2005) to try to answer the question of to what extent the biota is the product of dispersal events or can be seen as a vicariant, isolated biota (long isolation since the break-up of Gondwanaland). Based on these studies it has become apparent that the present biota of New Zealand is mostly the product of colonization and diversification, considerably postdating the break-up of Gondwanaland, and much more geologically recent (Goldberg et al., 2008; Wallis & Trewick, 2009). New Zealand is nevertheless a very interesting system to study these sorts of issues because it has characteristics of both a continent and an island (Daugherty, 1993). Assumptions about the development of the biota cannot be made purely on the basis of geological scenarios, as has been the case for some truly oceanic islands such as Hawaii. Although some biogeographers have until recently pursued a biogeographic programme centred on the belief that New Zealand is an ancient land and its biota is thus ancient too, New Zealand’s turbulent geological history is too complex and in some respects uncertain (Campbell & Hutching, 2007). A major advance in understanding is starting to pervade the biological community in recognition that the geological history of the Zealandian continent is in many respects quite distinct from the geological history of the New Zealand archipelago (Trewick et al. 2007, Campbell & Hutching, 2007). Whatever the fate of the biota that must have existed on Zealandia when it separated from Gondwanaland, the biology of New Zealand today reflects the geophysical history since the start of the Miocene. It remains unclear whether Zealandia was entirely submerged before the emergence of New Zealand, driven by tectonic activity on the Australian/Pacific plate boundary (~25 Ma), but the biological signature is that few lineages survived. Tectonic activity that began the formation of New Zealand resulted in movement of rock terraines and land areas with respect to one another, the formation of the Southern Alps and other mountain ranges, the submergence of some areas and considerable volcanic activity especially in North Island, which, together with climate cycling during the Pleistocene can be expected to have substantially influenced the countries biology. It is no surprise therefore that the nature of the New Zealand biota is complex and uniform patterns are few.

In order to properly understand the way the current biota could have evolved, we need to understand the fine scale processes that influence population structure and speciation. Thus, this thesis informs on the phylogeography and population genetic structure of a set of terrestrial

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animal taxa in New Zealand and accompanying islands. Results indicate that much of the speciation and radiation in the examined taxa is very recent and cannot be explained by long isolation. Assumption about the age of New Zealand islands and thus their biota are found to be false, but patterns of speciation are shown to vary considerable among taxa and across space. In some groups, physical isolation appears to have been required to allow speciation (e.g.

Talitropsis - chapter VI) with contiguous habitat occupied by a single species. Such cases very likely also indicate a role of extinction, loss of diversity in some regions, although identifying this directly is not possible. Other taxa (e.g. Mecodema beetles – chapter III) have responded quite differently to the same spatial and geophysical history; the huge diversity in New Zealand where most species have narrow spatial and habitat ranges might lead to the expectation that this genus would respond to dispersal to and colonisation of the Chatham Islands by prominent speciation, but this has not been the case. The same is true at a larger geographic scale; some lineages have close sister taxa in Australia and shallow genetic distances within and between species (e.g. Phaulacridium grasshoppers - chapter V) while others show deeper divergence to Australia, but relatively shallow speciation within New Zealand (Mecodema beetles - chapter III).

Analysis of relatively fine scale phylogeography also informs to the way inferences are made about the role of vicariant and dispersal events, and in particular to consider how extinction of lineages might lead to the false inference of ancient lineages. One example is the New Zealand woodpigeon, Hemiphaga, that exhibits low genetic divergence between populations in the New Zealand region including islands substantially distanced from one another, yet having deep phylogenetic divergence from its closest living relatives (chapter IV). Such a pattern is consistent with colonization in geologically recent times where it is accompanied by extinction of sister lineages elsewhere. At a fine scale, it is notable that, examination of taxa with prominent species diversity yields evidence of spatial and taxonomic monophyly and correlation of diversity with area, but taxon groups lacking species diversity reveal how this process most likely works. Even with mitochondrial data which suffers from having a small effective population size (i.e. understimating actual diversity), there is ample evidence (e.g. Phaulacridium - chapter V and

Anisolabis - chapter VI) that colonisation of islands involves many individuals (and possibly sustained gene flow). This implies that within taxon diversity is lost over time after colonisation, rather than as a result of dispersal. Such an observation indicates a change in emphasis is needed in biogeography, away from considering dispersal (and its perceived rarity) to considering much more the factors that effect establishment, population expansion and adaptation.

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Future work

There undoubtedly is the need for more molecular studies of the biota of New Zealand, to understand its origin and diversification patterns, as biogeographic interpretations based solely on observations of animal distributions can often be misleading. One important addition would be to include related taxa that are not from New Zealand into analyses, like Australia, New Caledonia and the Pacific, to advance the knowledge of the biotic relationships within the Australasian region and to be able to draw inferences on colonization events. This will also allow a comparative approach to phylogeogaphy as presented in this thesis. Furthermore it is important to better understand the mechanisms that drive dispersal and establishment of taxa and test for dispersal against vicariance scenarios in taxa with similar and different ecological traits, and to assess either congruence or incongruence of phylogeographic patterns in the biotic assemblage of these lineages. Additionally ecological and physiological studies could help to better understand the present biotic assemblage of New Zealand, as responses to geological and climatic factors play a major role in habitat occupancy, extinction, radiation and colonization of lineages. Further work should also focus on multi-gene approaches as different genes contain different information for phylogenetic reconstruction and timing of radiation or colonization events. Paradoxically, to better understand the historic processes that have governed the development of the extant biota, requires an improved understanding of populations, both in terms of their ecology and genetics. Understanding how populations respond to distant and changing opportunity will allow much better assessment of the likelihood of lineage loss over deeper time.

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APPENDIX I