Chrissen E.C. Gemmill

The diverse origins of New Zealand house mice

Molecular markers and morphological characters can help infer the colonization history of organisms. A combination of mitochondrial (mt) d-loop DNA sequences, nuclear DNA data, external measurements and skull characteristics shows that house mice (Mus musculus) in New Zealand and its outlying islands are descended from very diverse sources. The predominant genome is Mus musculus domesticus (from western Europe), but Mus musculus musculus (from central Europe) and Mus musculus castaneus (from southern Asia) are also represented genetically. These subspecies have hybridized to produce combinations of musculus and domesticus nuclear DNA coupled with domesticus mtDNA, and castaneus or musculus mtDNA with domesticus nuclear DNA. The majority of the mice with domesticus mtDNA that we sampled had d-loop sequences identical to two haplotypes common in Britain. This is consistent with long-term British–New Zealand cultural linkages. The origins of the castaneus mtDNA sequences widespread in New Zealand are less easy to identify.

Increased inter-colony fusion rates are associated with reduced COI haplotype diversity in an invasive colonial ascidian Didemnum vexillum.

Considerable progress in our understanding of the population genetic changes associated with biological invasions has been made over the past decade. Using selectively neutral loci, it has been established that reductions in genetic diversity, reflecting founder effects, have occurred during the establishment of some invasive populations. However, some colonial organisms may actually gain an ecological advantage from reduced genetic diversity because of the associated reduction in inter-colony conflict. Here we report population genetic analyses, along with colony fusion experiments, for a highly invasive colonial ascidian, Didemnum vexillum. Analyses based on mitochondrial cytochrome oxidase I (COI) partial coding sequences revealed two distinct D. vexillum clades. One COI clade appears to be restricted to the probable native region (i.e., north-west Pacific Ocean), while the other clade is present in widely dispersed temperate coastal waters around the world. This clade structure was supported by 18S ribosomal DNA (rDNA) sequence data, which revealed a one base-pair difference between the two clades. Recently established populations of D. vexillum in New Zealand displayed greatly reduced COI genetic diversity when compared with D. vexillum in Japan. In association with this reduction in genetic diversity was a significantly higher inter-colony fusion rate between randomly paired New Zealand D. vexillum colonies (80%, standard deviation ±18%) when compared with colonies found in Japan (27%, standard deviation ±15%). The results of this study add to growing evidence that for colonial organisms reductions in population level genetic diversity may alter colony interaction dynamics and enhance the invasive potential of newly colonizing species.

Molecular and morphological agreement in Pittosporaceae: phylogenetic analysis with nuclear ITS and plastid trnL–trnF sequence data

Pittosporaceae are a small family of flowering plants largely restricted to Australia, and entirely limited to the paleotropics. Two independent molecular datasets have been constructed with a representative sample from all nine genera of Pittosporaceae to test phylogenetic relationships suggested by recent morphological studies and to examine current morphological delimitations of genera. DNA sequence data derived from the ITS region of nuclear rDNA and from the trnL–trnF region of the chloroplast genome agree in uniting all species sampled from Pittosporum within a single clade, together with all species sampled from the previously segregated genus Citriobatus. Molecular data also confirm that members of the recently established genus Auranticarpa must be excluded from Pittosporum, and that another segregate genus, Sollya, should be placed within Billardiera. Hymenosporum remains a distinct, single-taxon lineage and Rhytidosporum is also confirmed as distinct. In most respects, our results are in agreement with recent taxonomic revisions based on morphology, and support an Australian origin of Pittosporaceae. Multiple dispersal events of Pittosporum from Australia to the islands of the Pacific and Indian Oceans, including New Zealand, are suggested, as well as island hopping throughout the Pacific.

Molecular support for Pleistocene persistence of the continental Antarctic moss Bryum argenteum

Abstract We examined sequence variation of ITS and phy2 for Bryum argenteum from Antarctica, sub-Antarctic, New Zealand and Australia to understand better taxonomic delimitations and resolve relationships between these geographic regions. Bryum argenteum has been recorded as two species, B. argenteum and B. subrotundifolium, in all four regions with the latter now referred to as B. argenteum var. muticum. We found disagreement between taxon delimitations (based on morphology) and molecular markers. All continental Antarctic specimens consistently formed a monophyletic sister group that consisted of both morphologically identified B. argenteum varieties, separate to all non-Antarctic specimens (also consisting of both varieties). We suggest, contrary to previous records, that all continental Antarctic (Victoria Land) populations are referable to B. argenteum var. muticum, while sub-Antarctic, Australian and New Zealand populations included here are B. argenteum var. argenteum. Additionally, since there was less genetic diversity within Victoria Land, Antarctica, than observed between non-Antarctic samples, we suggest that this is, in part, due to a potentially lower rate of DNA substitution and isolation in northern and southern refugia within Victoria Land since the Pleistocene.

A new record of Percursaria percursa (Ulvaceae, Ulvales) on the North Island, New Zealand

Abstract The filamentous green alga Percursaria percursa (Ulvaceae, Ulvales) was recorded for the first time on the North Island of New Zealand at Ōmokoroa Estuary, Tauranga Harbour. This species is previously known within New Zealand from only two records, both from the South Island. In Tauranga Harbour, this species was restricted to anoxic estuarine sediments where mangrove forests had been mulched, and mulchate left in situ. Percursaria percursa was found intertwined with Ulva spp. and Rhizoclonium spp. Surveys of other North and South Island estuaries suggest that this alga, although occurring as part of nuisance green algal blooms in Tauranga Harbour, has only colonized human-impacted locations, and has not yet been observed in ‘natural’ estuarine ecosystems in New Zealand. As this species was found intertwined with other mat-forming filamentous green algae, it can easily be misidentified in the field, leading to both over- and under-reporting of species occurrence.

Biological flora of New Zealand 13. Pittosporum cornifolium, tāwhiri karo, cornel-leaved pittosporum

A comprehensive review of the morphology, anatomy, taxonomy, chemistry and ecology of the endemic New Zealand facultative shrub epiphyte Pittosporum cornifolium (Pittosporaceae) is presented. Strong habitat specificity restricts this species to lowland forest and coastal habitats, which are widely yet discontinuously distributed north of latitude 42°15′S. Pittosporum cornifolium is typically associated with old growth forest systems and low nutrient substrates, with low mean daily temperatures in the coldest month (<0.6 °C) and high mean October vapour pressure deficits (>0.5 kPa) apparently restricting its distribution. Significant morphological variability is evident in leaves and flowers, especially with respect to plants from the Poor Knights Islands. Genetic analyses of five mainland populations and individuals representing Poor Knights Islands populations revealed relatively low genetic diversity at the population level which is likely to be the result of geographic isolation. Molecular phylogenetic studies suggest a New Caledonian origin for the species with close affinities to both P. pimeleoides subspecies. Several lines of evidence suggest recognition of the Poor Knights Islands entity as a new taxon. However, analysis of additional morphological, reproductive and molecular data across the full geographic range will be required to confirm current inferences. Although populations have declined, P. cornifolium is not currently threatened, however, it should be considered for reintroduction to sites in districts where its range has been severely reduced.

A New Species of Pittosporum Described from the Poor Knights Islands, Northland, Aotearoa/New Zealand

Abstract Here we describe Pittosporum roimata, the only vascular plant endemic to the Poor Knights Islands, Northland, Aotearoa/New Zealand. This new species has previously been referred to as a distinct yellow-flowered variant of Pittosporum cornifolium (tāwhiri karo, wharewhareatua), a morphologically similar epiphytic shrub known from both main islands of New Zealand as well as other offshore islands. We have segregated this new species from P. cornifolium based on morphology, DNA sequence variation, as well as distribution. Pittosporum roimata is distinguished from P. cornifolium by flowers with yellow petals, larger inflorescences, and producing several terminal fruits per stem. Herbarium specimens of P. roimata statistically have larger leaves and shorter petioles than specimens of P. cornifolium. Pittosporum roimata is locally common on the islands of Tawhiti Rahi, Aorangi, and Aorangaia, growing on rocky substrates associated with Xeronema callistemon (raupo taranga) and Metrosideros excelsa (pōhutukawa). Using the current New Zealand Threat Classification System, we suggest a preliminary classification of this new species as ‘at risk/naturally uncommon’ qualified data poor [DP], one location [OL].

Diet selectivity in a terrestrial forest invertebrate, the Auckland tree wētā, across three habitat zones.

Abstract Insects are important but overlooked components of forest ecosystems in New Zealand. For many insect species, information on foraging patterns and trophic relationships is lacking. We examined diet composition and selectivity in a large‐bodied insect, the Auckland tree wētā Hemideina thoracica, in three habitat zones in a lowland New Zealand forest. We asked whether H. thoracica selectively forage from available plant food sources, and whether these choices were lipid‐rich compared to nonpreferred available plants. We also identified the proportion of invertebrates in their frass as a proxy for omnivory. From reconnaissance plot sampling, together with fecal fragment analysis, we report that more than 93% of individual tree wētā had eaten invertebrates before capture. Additionally, wētā in the highest elevation hillslope habitat zone consumed significantly fewer species of plants on average than wētā on the low‐elevation terrace habitat. Upper hillslope wētā also had the highest average number of invertebrate fragments in their frass, significantly more than wētā in the low‐elevation terrace habitat zone. Wētā showed high variability in the consumption of fruit and seeds across all habitat zones. Generally, we did not observe diet differences between the sexes (although it appears that male wētā in the mid‐hillslope habitat ate fruits and seeds more voraciously than females), suggesting that the sexes have similar niche breadths and display similar degrees of omnivorous behavior. Extraction of leaf lipids demonstrated a range of lipid content values in available plants, and Ivlevs Electivity Index indicated that plant species which demonstrated high electivity tended to have higher concentrations of lipids in their leaves. Our findings indicate that H. thoracica forage omnivorously and selectively, and hence play multiple roles in native ecosystems and food webs.

Genetic diversity and structure in the Philippine Rafflesia lagascae complex (Rafflesiaceae) inform its taxonomic delimitation and conservation

Abstract Rafflesia lagascae is a rare endo-holoparasitic species with a disjunct distribution on Luzon Island. It is morphologically very similar to R. manillana from nearby Samar. This study aims to contribute to the taxonomy and conservation of R. lagascae and R. manillana (i.e. the R. lagascae complex) by resolving their patterns of genetic diversity and structure. The results of analyses of a microsatellite data set indicate that despite their frequently extremely small sizes and geographic isolation, Rafflesia populations display moderate genetic diversity and do not show evidence of pronounced inbreeding. Most populations appear to have limited gene flow among them. Patterns of genetic diversity of staminate and pistillate Rafflesia flowers growing on the same Tetrastigma host plants indicate that the R. lagascae complex is monoecious and that host plants are regularly infected by multiple Rafflesia plants. PCoA and Bayesian cluster analyses show that the complex is composed of three genetically isolated taxa. One of these constitutes R. manillana, supporting the morphology-based hypothesis that it is taxonomically distinct from R. lagascae. The second taxon in this complex is composed of a morphologically cryptic R. lagascae population from Mt. Labo, which is genetically distinct from all remaining R. lagascae populations that were studied and that form the third taxon. We recommend that these three taxa are managed as different conservation entities.

A preliminary conservation genetic study of Pittosporum obcordatum (Pittosporaceae), an endemic New Zealand species with a disjunct distribution

ABSTRACT Pittosporum obcordatum (Pittosporaceae; heart-leaved kōhūhū) is an endemic New Zealand plant species that is classified as Threatened–Nationally Vulnerable. It has a disjunct distribution and is only known from relatively few and small populations. Using 10 Inter-Simple Sequence Repeat markers (ISSRs), we studied patterns of genetic diversity and genetic differentiation among eight out of the c. 14 populations of this species to inform its conservation management. Pittosporum obcordatum has low genetic diversity at the population level (uHe = 0.169) compared to other long-lived and outcrossing species, but genetic diversity is relatively high in comparison with several other threatened species. Spearman’s Rank Correlation Coefficients suggest significant positive correlations between population size and genetic diversity as measured by the percentage of polymorphic loci and uHe. Pittosporum obcordatum also shows relatively high levels of genetic differentiation among populations (AMOVA-derived , P < 0.001; all pairwise Φst values P < 0.05), indicating low genetic connectivity. Populations with relatively few plants are therefore prone to further reductions in genetic diversity through inbreeding and genetic drift. Of these, especially the Kaitaia, Owen Valley and Paengaroa populations are of conservation concern, because they contain private alleles, and therefore notably contribute to the genetic diversity of P. obcordatum.