Impacts of the Pliocene and Pleistocene glaciations on genetic diversity among New Zealand and Antarctic Arthropods
Notice bibliographique
Résumé
Geological events such as glaciation and crustal uplift can impact on species' distributions and genetic diversity through the formation of dispersal barriers and fragmentation of habitat. This thesis investigates the effects of the Pliocene and Pleistocene glaciations on intra- and interspecific population diversity in a New Zealand aquatic invertebrate and an Antarctic terrestrial invertebrate. Caddisflies (Insecta: Trichoptera) are an aquatic invertebrate that are widespread and common throughout both islands of New Zealand. Species are used in stream health studies and as a measure of diversity, but knowledge of their genetic diversity is limited. Mitochondrial DNA (COI) sequence variability was used to examine levels of divergence among closely-related species of caddisflies collected from throughout New Zealand. Based on genetic analysis, seven closely related species pairs were identified, consisting of morphologically distinct species, each restricted to either the North or South Island. Another five species showed similar or greater levels of "intraspecific" divergence, with genetically distinct populations on each island. Sequence divergence between these twelve "species pairs" ranged from 0.41% in Confluens olingoides / Confluens hamiltoni, to 9.92% between the North and South Island populations of Pycnocentria evecta. Based on molecular clock estimates, divergences for these twelve species pairs were estimated to within the last 5 million years, with most dating to the beginning of the Pleistocene (2 Mya). I conclude that population fragmentation during the Pleistocene glaciations and subsequent closing of the Cook Strait land bridge have both played important roles in the isolation and speciation of the New Zealand caddisflies. Mitochondrial DNA (COI) analysis was also used to examine the levels of genetic variability within and among populations of three endemic springtail species (Arthropoda: Collembola), collected from the Mackay Glacier region of southern Victoria Land, in the Ross Dependency, Antarctica. I tested the hypothesis that genetic divergences would occur among glacially-isolated habitats within a fragmented landscape. Mitochondrial analysis of 97 individuals showed high levels of genetic divergence at small spatial scales (<15km). High levels of genetic divergence were found among populations for two of the three species. Gomphiocephalus hodgsoni, a widespread and common species showed 7.6% sequence divergence on opposite sides of the Mackay Glacier. Similar divergences were also found for Neocryptopygus nivicolus, a more range-restricted species showing 4.0% sequence divergence among populations. Based on molecular clock estimates, divergence of these populations occurred in the last 5 Mya. It was suggested that glaciations during the Pliocene (5-2 Mya) and throughout the Pleistocene (2 Mya - 10 Kya) have fragmented springtail populations in this region and isolated them in small, refugial nunataks. I conclude that glaciation has promoted and maintained the levels of diversity observed among populations of springtails and that isolation has occurred on extremely small spatial scales. Collectively, the two studies presented here suggest that the Pleistocene glaciations are responsible for habitat fragmentation, the genetic signatures for which can be observed in invertebrate taxa in both New Zealand and southern Victoria Land, Antarctica.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,001 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,001 | 0,001 |
| Études des sciences et des technologies | 0,001 | 0,001 |
| Communication savante | 0,001 | 0,000 |
| Science ouverte | 0,000 | 0,001 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,003 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».