Floristic homogenization of South Pacific islands commenced with human arrival.

The increasing similarity of plant species composition among distinct areas is leading to the homogenization of ecosystems globally. Human actions such as ecosystem modification, the introduction of non-native plant species and the extinction or extirpation of endemic and native plant species are considered the main drivers of this trend. However, little is known about when floristic homogenization began or about pre-human patterns of floristic similarity. Here we investigate vegetation trends during the past 5,000 years across the tropical, sub-tropical and warm temperate South Pacific using fossil pollen records from 15 sites on 13 islands within the biogeographical realm of Oceania. The site comparisons show that floristic homogenization has increased over the past 5,000 years. Pairwise Bray-Curtis similarity results also show that when two islands were settled by people in a given time interval, their floristic similarity is greater than when one or neither of the islands were settled. Importantly, higher elevation sites, which are less likely to have experienced human impacts, tended to show less floristic homogenization. While biotic homogenization is often referred to as a contemporary issue, we have identified a much earlier trend, likely driven by human colonization of the islands and subsequent impacts.

Herd management and subsistence practices as inferred from isotopic analysis of animals and plants at Bronze Age Politiko-Troullia, Cyprus.

The Bronze Age village of Politiko-Troullia, located in the foothills of the copper-bearing Troodos mountains of central Cyprus, was occupied ~2050-1850 cal BCE. Excavated evidence shows that community activities included copper metallurgy (ore processing, smelting and casting), crop cultivation, and rearing of livestock. Faunal analysis reveals day-to-day subsistence practices that included consumption of sheep, goat, cattle, and pig, as well as community-scale ritual feasting focused on fallow deer, Dama dama mesopotamica. In this paper, we present bone collagen stable isotope data from these taxa to infer how these animals were managed. We incorporate stable isotope baselines calculated from modern cereal grains and compare these to archaeological seeds from Politiko-Troullia. Mean values of δ13C and δ15N cluster for livestock consistent with a diet of C3 plants, with a wider range in goats that suggests free-browsing herds. Higher δ15N values in cattle may reflect supplemental feeding or grazing in manured fields. Plant isotope values suggest livestock diets were predominantly composed of cultivated taxa. In contrast, deer and pig bones produce more negative mean δ13C and δ15N values suggesting that the villagers of Politiko-Troullia complemented their management of domesticated animals with hunting of wild deer and feral pigs in the woodlands surrounding their village.

Human arrival and landscape dynamics in the northern Bahamas.

The first Caribbean settlers were Amerindians from South America. Great Abaco and Grand Bahama, the final islands colonized in the northernmost Bahamas, were inhabited by the Lucayans when Europeans arrived. The timing of Lucayan arrival in the northern Bahamas has been uncertain because direct archaeological evidence is limited. We document Lucayan arrival on Great Abaco Island through a detailed record of vegetation, fire, and landscape dynamics based on proxy data from Blackwood Sinkhole. From about 3,000 to 1,000 y ago, forests dominated by hardwoods and palms were resilient to the effects of hurricanes and cooling sea surface temperatures. The arrival of Lucayans by about 830 CE (2σ range: 720 to 920 CE) is demarcated by increased burning and followed by landscape disturbance and a time-transgressive shift from hardwoods and palms to the modern pine forest. Considering that Lucayan settlements in the southern Bahamian archipelago are dated to about 750 CE (2σ range: 600 to 900 CE), these results demonstrate that Lucayans spread rapidly through the archipelago in less than 100 y. Although precontact landscapes would have been influenced by storms and climatic trends, the most pronounced changes follow more directly from landscape burning and ecosystem shifts after Lucayan arrival. The pine forests of Abaco declined substantially between 1500 and 1670 CE, a period of increased regional hurricane activity, coupled with fires on an already human-impacted landscape. Any future intensification of hurricane activity in the tropical North Atlantic Ocean threatens the sustainability of modern pine forests in the northern Bahamas.

Vascular plant species of the Kingdom of Tonga by vegetation type, species origin, growth form, and dispersal mechanism.

The aim of this research is to compile a database of vascular plants found in the Kingdom of Tonga in western Polynesia, a phyto-geographic subregion of the South Pacific. The Tongan islands are spread over ~600,000 km2 of the Pacific Ocean between 15-23° S latitude and 173-177° W longitude. The archipelago is comprised of 171 islands with an aggregate land area of about 720 km2 . Since there is no comprehensive or updated flora for Tonga, we use 143 published sources to compile a database for 1,020 plant species, of which more than 450 are indigenous to these islands. Tonga is noteworthy for its low proportion of endemics, accounting for <5% of the indigenous species and <2% of the total plant species. Our database documents species presence in Tonga as a whole, and more specifically on 11 Tongan islands or island groups. We have assembled ecological information for each plant species according to growth form, vegetation type, origin (endemic, indigenous, and introduced species), and dispersal mechanisms. We include introduced species in our database because they represent over half of the plant species growing in Tonga. Species origins reflect human alteration of Tongan ecosystems in which endemic and indigenous species represent pre-human vegetation and introduced species indicate plants brought by either Polynesian or European settlers. For example, on Tongatapu, the largest and longest occupied island, more than half the plants are introduced, whereas on the sparsely populated, more remote islands, 70-90% of the species are indigenous. Dispersal mechanisms, which may include more than one mechanism per species, are documented in over 100 publications. Our database provides information on the whole suite of plant dispersal mechanisms over entire communities or island groups in Tonga. Plant species dispersal differs across environmental variables, including island geology, topography, vegetation type, and species origin. The older limestone islands have more bird, water, and human-dispersed plants, while the youngest volcanic islands have the most wind-dispersed species. Our database documents plant species endemism, introductions, vegetation types and dispersal mechanisms that reveal key biogeographic dynamics of the Tongan archipelago in the South Pacific. Please cite this Ecology Data Paper if the data are used in publication, presentation, or teaching activities. There are no copyright restrictions.

Economic and social activities on ancient Cypriot terraced landscapes.

We investigate ancient agricultural terraces and their associated social and economic activities across the site complex consisting of the village at Politiko-Troullia and its more extensive associated taskscape. Surface artifact distributions mapped over 12 ha are integrated with evidence excavated from this Bronze Age settlement in central Cyprus. Contrary to expectations, artifact densities do not diminish with distance from the village architecture. In particular, concentrations of Prehistoric Bronze Age ceramics and ground stone artifacts are most pronounced on nearby terraced hillsides. These terraces were not utilized for domestic structures, but for extensive processing of agricultural crops and copper ore. Bronze Age excavated plant remains indicate cultivation of olives, grapes and figs, with wood resources dominated by olive and pine. Larger, non-portable ground stones and gaming stones are associated with communal social and economic activities in open courtyard settings in Politiko-Troullia. This category of ground stone also is particularly common on the terraced hillsides around Troullia, suggesting that similar behaviors occurred beyond village structures. The terraced landscape of Politiko-Troullia exemplifies a multi-faceted taskscape with a range of agricultural, metallurgical and social activities.

The intertropical convergence zone modulates intense hurricane strikes on the western North Atlantic margin.

Most Atlantic hurricanes form in the Main Development Region between 9°N to 20°N along the northern edge of the Intertropical Convergence Zone (ITCZ). Previous research has suggested that meridional shifts in the ITCZ position on geologic timescales can modulate hurricane activity, but continuous and long-term storm records are needed from multiple sites to assess this hypothesis. Here we present a 3000 year record of intense hurricane strikes in the northern Bahamas (Abaco Island) based on overwash deposits in a coastal sinkhole, which indicates that the ITCZ has likely helped modulate intense hurricane strikes on the western North Atlantic margin on millennial to centennial-scales. The new reconstruction closely matches a previous reconstruction from Puerto Rico, and documents a period of elevated intense hurricane activity on the western North Atlantic margin from 2500 to 1000 years ago when paleo precipitation proxies suggest that the ITCZ occupied a more northern position. Considering that anthropogenic warming is predicted to be focused in the northern hemisphere in the coming century, these results provide a prehistoric analog that an attendant northern ITCZ shift in the future may again return the western North Atlantic margin to an active hurricane interval.