Journal Articles

Permanent URI for this collectionhttps://mro.massey.ac.nz/handle/10179/7915

Browse

Subject: search.filters.subject.ECOLOGY

Search Results

Now showing 1 - 4 of 4
  • Thumbnail Image
    Item
    Origin and post-colonization evolution of the Chatham Islands skink (Oligosoma nigriplantare nigriplantare).
    (WILEY-BLACKWELL, 2008-07) Liggins L; Chapple DG; Daugherty CH; Ritchie PA
    Island ecosystems provide an opportunity to examine a range of evolutionary and ecological processes. The Chatham Islands are an isolated archipelago situated approximately 800 km east of New Zealand. Geological evidence indicates that the Chatham Islands re-emerged within the last 1-4 million years, following a prolonged period of marine inundation, and therefore the resident flora and fauna is the result of long-distance overwater dispersal. We examine the origin and post-colonization evolution of the Chatham Islands skink, Oligosoma nigriplantare nigriplantare, the sole reptile species occurring on the archipelago. We sampled O. n. nigriplantare from across nine islands within the Chatham Islands group, and representative samples from across the range of its closest relative, the New Zealand mainland common skink (Oligosoma nigriplantare polychroma). Our mitochondrial sequence data indicate that O. n. nigriplantare diverged from O. n. polychroma 5.86-7.29 million years ago. This pre-dates the emergence date for the Chatham Islands, but indicates that O. n. nigriplantare colonized the Chatham Islands via overwater dispersal on a single occasion. Despite the substantial morphological variability evident in O. n. nigriplantare, only relatively shallow genetic divergences (maximum divergence approximately 2%) were found across the Chatham Islands. Our analyses (haplotypic diversity, Phi(ST), analysis of molecular variance, and nested clade phylogeographical analysis) indicated restricted gene flow in O. n. nigriplantare resulting in strong differentiation between islands. However, the restrictions to gene flow might have only arisen recently as there was also a significant pattern of isolation by distance, possibly from when the Chatham Islands were a single landmass during Pleistocene glacial maxima when sea levels were lower. The level of genetic and morphological divergence between O. n. nigriplantare and O. n. polychroma might warrant their recognition as distinct species.
  • Thumbnail Image
    Item
    Exploring the sociobiology of pyoverdin-producing Pseudomonas.
    (WILEY-BLACKWELL, 2013-11) Zhang X-X; Rainey PB
    The idea that bacteria are social is a popular concept with implications for understanding the ecology and evolution of microbes. The view arises predominately from reasoning regarding extracellular products, which, it has been argued, can be considered "public goods." Among the best studied is pyoverdin-a diffusible iron-chelating agent produced by bacteria of the genus Pseudomonas. Here we report the de novo evolution of pyoverdin nonproducing mutants, genetically characterize these types and then test the appropriateness of the sociobiology framework by performing growth and fitness assays in the same environment in which the nonproducing mutants evolved. Our data draw attention to discordance in the fit between social evolution theory and biological reality. We show that pyoverdin-defective genotypes can gain advantage by avoiding the cost of production under conditions where the molecule is not required; in some environments pyoverdin is personalized. By exploring the fitness consequences of nonproducing types under a range of conditions, we show complex genotype-by-environment interactions with outcomes that range from social to asocial. Together these findings give reason to question the generality of the conclusion that pyoverdin is a social trait.
  • Thumbnail Image
    Item
    A SINE of restricted gene flow across the Alpine Fault: phylogeography of the New Zealand common skink (Oligosoma nigriplantare polychroma).
    (WILEY-BLACKWELL, 2008-08) Liggins L; Chapple DG; Daugherty CH; Ritchie PA
    New Zealand has experienced a complex climatic and geological history since the Pliocene. Thus, identifying the processes most important in having driven the evolution of New Zealand's biota has proven difficult. Here we examine the phylogeography of the New Zealand common skink (Oligosoma nigriplantare polychroma) which is distributed throughout much of New Zealand and crosses many putative biogeographical boundaries. Using mitochondrial DNA sequence data, we revealed five geographically distinct lineages that are highly differentiated (pairwise Phi(ST) 0.54-0.80). The phylogeographical pattern and inferred age of the lineages suggests Pliocene mountain building along active fault lines promoted their divergence 3.98-5.45 million years ago. A short interspersed nuclear element (SINE) polymorphism in the myosin gene intron (MYH-2) confirmed a pattern of restricted gene flow between lineages on either side of the mountain ranges associated with the Alpine Fault that runs southwest to northeast across the South Island of New Zealand. An analysis of molecular variance confirmed that approximately 40% of the genetic differentiation in O. n. polychroma is distributed across this major fault line. The straits between the main islands of New Zealand accounted for much less of the variation found within O. n. polychroma, most likely due to the repeated existence of landbridges between islands during periods of the Pleistocene that allowed migration. Overall, our findings reveal the relative roles of different climatic and geological processes, and in particular, demonstrate the importance of the Alpine Fault in the evolution of New Zealand's biota.
  • Thumbnail Image
    Item
    Biotic impacts of energy development from shale: Research priorities and knowledge gaps
    (ECOLOGICAL SOC AMER, 1/01/2014) Souther S; Tingley MW; Popescu VD; Hayman DTS; Ryan ME; Graves TA; Hartl B; Terrell K
    Although shale drilling operations for oil and natural gas have increased greatly in the past decade, few studies directly quantify the impacts of shale development on plants and wildlife. We evaluate knowledge gaps related to shale development and prioritize research needs using a quantitative framework that includes spatial and temporal extent, mitigation difficulty, and current level of understanding. Identified threats to biota from shale development include: surface and groundwater contamination; diminished stream flow; stream siltation; habitat loss and fragmentation; localized air, noise, and light pollution; climate change; and cumulative impacts. We find the highest research priorities to be probabilistic threats (underground chemical migration; contaminant release during storage, during disposal, or from accidents; and cumulative impacts), the study of which will require major scientific coordination among researchers, industry, and government decision makers. Taken together, our research prioritization outlines a way forward to better understand how energy development affects the natural world. © The Ecological Society of America.