Assessing factors influencing the spatial distribution of species diversity in ground dwelling ant assemblages in lowland, wet forest of southwest Sri Lanka

Tropical forests of the world are fast disappearing and there is a race to understand patterns of species distribution in space and time. Studying species distributions can provide better frameworks for conservation of these ecologically important patches of floral and faunal diversity. The island of Sri Lanka is a well known harbour of unique and highly threatened biodiversity. Tropical lowland forest is remnant in the south-west of the island now mainly existing in small patches. While most are small disturbed fragments, Sinharaja Forest Reserve represents one of the largest remaining patches of this important ecosystem. As a UNESCO World Heritage Site and a Man and Biosphere Reserve, it has a dual role as a conservation area and a historically important resource forest. While the distribution of vegetation diversity has been well documented, analyses of invertebrate species distributions are lacking. This thesis investigated a key arthropod group, ground dwelling ants, in relation to environmental gradients within the forest. Cumulative results demonstrate the high diversity of the forest patch. In an area representing less than half the reserve, over 173 ground dwelling ant species were found in distinct assemblages throughout the forest. Since the forest is located upon a series of parallel ridges, ant species distribution was first analysed in terms of this small elevation change. Species richness declined over a vertical incline from 430 m to 660 m, highlighting a possible small-scale, mountain mass effect. This section of the reserve is also characterised by a patch of once-logged forest (30 years previously). A study was undertaken to investigate whether there were residual effects of selective logging on the reserve.Significant differences between species assemblages in once-logged forest and unlogged forest add to growing evidence that selectively logged forests continue to remain distinct from unlogged forest even after decades of regeneration. Ant distribution was then analysed for their relationship with habitat heterogeneity and tree species distribution. Long-term research on tree species in the SFR has demonstrated a close relationship to habitat complexity. Ant species appear to respond more to the structural heterogeneity of the vegetation than to actual topographic variation within the forest. From a conservation perspective, maintaining the integrity of this highly diverse forest is imperative. The impact of anthropogenic land uses surrounding the forest was investigated in terms of ant assemblages along the forest edges. Significant differences were found between assemblages within the edges bordered by different matrix types. Even relatively large forest remnants can be affected by the surrounding matrix land uses and encouraging the growth of structurally similar vegetation and maintaining low disturbance along the borders should attenuate the effect of the edge. Overall, the highly heterogeneous distribution of ant assemblages within the SFR demonstrates the potential for other small patches to be harbours of further species diversity. Future research should be undertaken to assess the diversity and distribution of ant species within this region and encourage the protection of this remnant diversity

A new species of Neocaeculus (Acari: Prostigmata: Caeculidae) from Barrow island, Western Australia, with a checklist of world Caeculidae

Neocaeculus imperfectus new species is described from material collected on Barrow Island, Western Australia. Keys to genera and Australasian species of Caeculidae are provided, and the relationship between the genera Neocaeculus and Microcaeculus is discussed. A checklist of species for Caeculidae is provided

Diversity and richness of ant species in a lowland wet forest reserve in Sri Lanka

Sinharaja Forest Reserve (SFR) represents one of the largest remaining stands of mixed dipterocarp forest in southwestern Sri Lanka. It is characterised by high floral and faunal endemicity and is gazetted as a World Heritage Site. Research was undertaken to study the ground-dwelling ants in the SFR using pitfall traps and leaf litter extraction. The collection was carried out in disturbed and undisturbed primary forest, old selectively-logged forest (30 years old) and periphery forest (agricultural buffer zone) along a small elevation gradient (200 m – 700 m). A total of 173 species and morphospecies in 11 subfamilies and 54 genera were caught. Pheidole and Tetramorium were the most speciose genera, with 19 and 18 species respectively; Cerapachys followed with 12 species. These results demonstrate the high diversity of litter dwelling ant species in the SFR. There were no significant differences in species richness between sites within the forest. Future studies should analyse species assemblages in each forest type in relation to forest structure and environmental parameters to further understand the distribution of ant species across this unique and complex forest

A revision of the ant genus Probolomyrmex (Hymenoptera: Formicidae: Proceratiinae) in Australia and Melanesia

Five species of the rarely encountered ant genus Probolomyrmex are known from Australia and Papua New Guinea, four of which are described here for the first time. Two species belong to the greavesi species-group (P. greavesi, P. latalongus sp. n.)while three belong to the longinodus species-group (P. aliundus sp. n., P. newguinensis sp. n., P. simplex sp. n.). The genus is now known to occur broadly across northern Australia and P. newguinensis and P. simplex are the first species of the genus described from Papua New Guinea. A key to Australian and Melanesian species is provided

Sequencing the ant fauna of a small island: Can metagenomic analysis enable faster identification for routine ant surveys?

All known ant species from a small Western Australian island were subjected to DNA barcoding of the CO1 gene, with a view to using the database to identify ants by Next Generation Sequencing in subsequent, routine surveys. A further aim was to evaluate whether the data could be used to see if any new species had arrived on the island since the total fauna had been inventoried. Of the 125 unique ant species then known from the island, 72 were successfully barcoded. Those that were refractory to amplification were largely the result of sample age and/or contamination. Following this base-line barcoding, ants were sampled from 14 regular sampling sites and ant sequences were obtained from the bulked ‘metagenomic soup’. Prior to doing this, a parataxonomist had identified all ant species in the samples and returned them to the ‘soup’. Successful identification for each site varied from 38% (Sites 12 and 27) to 100% of species (Site 10). Comparison of the number of species recovered with the number of sequences obtained from each sample showed a positive correlation between the two variables. When a site had >1,000 sequences, the average recovery rate was 79%, which is in contrast to the lowest four recovery rates (Site samples 12, 22, 26 and 27), which had fewer than 440 amplicon sequences. The ability to detect individuals that occur at low frequencies is also important. We analysed each site individually to determine if a species was detected and how that related to the proportion of individuals in the pooled sample. Where a species was present at <4% of the total sample, it was only detected 10% of the time, indicating that adequate sequencing depth is critical to species recovery. We conclude that this technique was only partially successful in replacing conventional taxonomy and that it could have limited ability to detect incursions unless the new arrival is abundant. Current barcoding is no longer limited to the CO1 gene and other genes are characterised for identification of intractable groups where CO1 does not provide appropriate levels of resolution

Arid zone ant communities of Western Australia

This thesis is prepared in three parts; the first part is a study of the ant species of the southern Carnarvon Basin, which was undertaken in order to determine the patterns of ant species distribution in this arid zone area. The distribution patterns were looked at in terms of biogeographical regions and they demonstrated the transitional nature of this particular area. Recommendations to alter the border between the South-west Province and the Eremaean Province were supported. The next chapter of this thesis analysed ant species from long unburnt and burnt areas of three main vegetation types (two Triodia species grasslands and Acacia aneura woodlands) in the Gibson Desert Nature Reserve. This study was carried out to observe the recovery of ant populations after fire. The results provided further evidence that invertebrates are measurably impacted by fire in the arid zone. The final chapter is a comparison of these two arid zone studies with six other ant community studies from throughout Western Australia. It demonstrated the uniqueness of some arid zone sites as well as related each study to each other according to their ant communities

Investigating residual effects of selective logging on ant species assemblages in Sinharaja Forest Reserve, Sri Lanka

The residual effects of logging on forest fauna and flora have been well studied in other regions of the world, with many investigations finding that recovery of species richness and abundance can occur within one or two decades after the logging event. In this study, we use ant assemblages to compare logged (>30 years) and unlogged mixed dipterocarp forest in the Sinharaja Forest Reserve, a World Heritage Site in Sri Lanka. Species richness and abundance were higher in the logged forest than in the unlogged forest, but not significantly so. Species assemblages, on the other hand, were significantly different and were associated with different environmental variables in the logged and unlogged forest. The findings from this study corroborate other studies that have shown that species composition in logged forest does not appear to return to unlogged forest composition, even after three to six decades have passed. Since this study was not a before-and-after comparison, it is difficult to confirm whether the differences arise from the residual effects of logging or from the general patchiness of species distribution in tropical forest. However, the cumulative results do suggest that there is a residual effect of logging on ant species composition in this forest, even after more than 30 years of regeneration

Correlates of ant (Hymenoptera: Formicidae) and tree species diversity in Sri Lanka

Variation in species diversity across a landscape can be attributed to a variety of spatial and temporal factors, as well as inter-specific interactions. In this study, ant species assemblages were investigated in relation to habitat heterogeneity and tree species assemblage in a lowland dipterocarp-dominated forest in Sri Lanka. We tested the hypothesis that ant species assemblages would follow the same patterns of distribution as tree species assemblages along a small elevational gradient. A total of 100 ground-dwelling ant species and 143 tree species were recorded in 0.6 ha. Forty percent of variation in the ant species assemblages could be attributed to variation in elevation and percent plant cover at ground level. Although tree species assemblages also responded strongly to changes in elevation, there was no significant relationship between ant and tree species diversity. In this particular forest, ant species responded to the same topographical variation as did tree species assemblages; however, the ant assemblages appear to be responding to plant structure at ground level rather than to tree species diversity per se. These results suggest that preserving topographical features in a landscape may enhance ant species diversity

The ant fauna of the Pilbara Bioregion, Western Australia

The ant fauna of the Pilbara Bioregion, which covers an area of ca. 179,000 km2, is reviewed. During surveys undertaken between May 2003 and September 2006, ants were one of the taxonomic groups to receive special attention. The total number of ant species recorded from 24 survey areas was 245, and these were placed in 37 genera and 9 subfamilies. Ants recorded from single quadrats (‘singletons’) accounted for 18.8% of the species. The most speciose genera were Camponotus (36 spp.), Iridomyrmex (31 spp.) and Melophorus (30 spp.). Based on current knowledge, 43% are purely Eremaean, 8% are primarily Bassian, 6% are primarily Torresian, nearly 17% occur over two of Australia’s three biogeographic divisions, and 25% are widespread over all three. At a quadrat level, there was no significant correlation between richness and any environmental variable, while clustering analysis revealed weak environmental correlations with ant assemblage composition. The classification at survey area level identified six groupings of ants; three climatic variables associated with these groupings were identified, namely annual temperature, precipitation in the coldest quarter of the year and annual precipitation

Revisiting the Psocoptera (Insecta) of Barrow Island, Western Australia

Courtenay Smithers recorded five species of Psocoptera on Barrow Island in 1982. Since then, repeated surveys have been conducted as part of environmental impact assessments associated with the Gorgon Project development on Barrow Island. This baseline information on invertebrates is to be utilised as a component of surveillance programs in support of the Gorgon Project's quarantine detection system. These additional surveys on the island have yielded a further 20 species of psocopterans, bringing the total fauna collected to 25 species. This includes the first Australian record of the synanthropic species 'Dorypteryx domestica' (Smithers)