International Journal of Molecular Zoology 2024, Vol.14, No.3, 128-140 http://animalscipublisher.com/index.php/ijmz 134 6.2 Phylogeographic patterns in relation to geological changes Geological changes have a profound impact on the phylogeographic patterns of invertebrates. In the Hawaiian archipelago, repeated colonization of new island groups has led to lineages progressing down the island chain, with the most ancestral groups on the oldest islands. Similarly, in New Zealand, phylogeographic studies reveal signatures of partitioning in various regions and expansion in different directions, influenced by Pliocene tectonic events and range expansion following the last glacial maximum (Trewick et al., 2011). In southeastern Australia, the interaction between physiogeographic landscape context and life history characteristics, particularly dispersal ability, has generated predictable outcomes for how species responded to Pleistocene climatic changes (Garrick et al., 2012). In unglaciated eastern North America, recurrent phylogeographic patterns, such as the Appalachian Mountain discontinuity and the Mississippi River discontinuity, are attributable to isolation and differentiation during Pleistocene glaciation. 6.3 Case studies: examples of speciation events Several case studies illustrate speciation events in invertebrates. In the Hawaiian terrestrial arthropods, speciation patterns are classified into three categories: single representatives of a lineage throughout the islands, species radiations with single endemic species on different volcanoes or islands, and single widespread species within a radiation of species that exhibit local endemism. In Tallaganda, southeastern Australia, flightless low-mobility forest invertebrates, such as springtails and terrestrial flatworms, exhibit spatial patterns of intraspecific genetic diversity that conform to topography-based divisions, highlighting cases of phylogeographic congruence and incongruence (Garrick et al., 2012). In European freshwater copepod crustaceans, deep mitochondrial splits among populations indicate that divergence of lineages predates the Pleistocene glaciations, suggesting that historical and biogeographical factors significantly shape modern patterns of distribution (Kochanova et al., 2021). Lastly, in Southern China, the Odorrana graminea sensu lato exhibits five major highly divergent lineages, with phylogenetic analyses revealing significant gene flow events and demographic expansions during the last glacial maximum (Chen et al., 2019). 7 Adaptation and Survival Strategies 7.1 Genetic adaptations to environmental stressors Invertebrates exhibit a range of genetic adaptations that enable them to survive and thrive in response to various environmental stressors. For instance, freshwater invertebrates have shown genetic changes in response to climate change, particularly in traits related to temperature and photoperiod adjustments (Stoks et al., 2013). Similarly, studies on pollution adaptation have highlighted the complex genetic responses to heavy metal contamination, although the evidence for consistent adaptive responses across different species remains mixed (Loria et al., 2019). Additionally, DNA methylation has been identified as a mechanism by which invertebrates can adjust to novel environments, such as urban settings, by altering stress response genes (Holdt et al., 2022). These genetic adaptations are crucial for maintaining homeostasis and ensuring survival in changing environments. 7.2 Evolution of reproductive and developmental strategies The evolution of reproductive and developmental strategies in invertebrates is a key aspect of their adaptation to environmental changes. Phenological shifts, such as changes in the timing of life cycle events, have been observed in response to climate change, driven by both genetic and plastic responses (Schilthuizen and Kellermann, 2013). In some cases, maladaptive plasticity can occur when ancestral developmental systems are co-opted to meet new environmental challenges, leading to reduced fitness. However, genetic compensation mechanisms can remodel these plastic responses to restore fitness (Velotta and Cheviron, 2018). This remodeling process is often one of the earliest steps in the adaptive evolution of reproductive and developmental strategies, allowing invertebrates to better cope with novel stressors. 7.3 Phenotypic plasticity and behavioral adaptations Phenotypic plasticity plays a significant role in the survival of invertebrates under environmental stress. This plasticity allows organisms to express different phenotypes depending on environmental conditions, thereby increasing their fitness and expanding their ecological niches (Hoffmann and Bridle, 2021). For example, thermal
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