Vegetation history at the multi-period prehistoric complex at Ballynahatty, Co. Down, Northern Ireland.

Palaeoecological methods can provide an environmental context for archaeological sites, enabling the nature of past human activity to be explored from an indirect but alternative perspective. Through a palynological study of a small fen wetland located within the catchment of a multi-period prehistoric complex at Ballynahatty, Co. Down, Northern Ireland, we reconstruct the vegetation history of the area during the early prehistoric period. The pollen record reveals tentative evidence for Mesolithic activity in the area at 6410-6220 cal. BC, with woodland disturbance identified during the Mesolithic-Neolithic transitional period ca. 4430-3890 cal. BC. A more significant impact on the landscape is observed in the Early Neolithic from 3944-3702 cal. BC, with an opening up of the forests and the establishment of a mixed agricultural economy. This activity precedes and continues to be evident during the Mid-Neolithic during which megalithic tombs and related burial sites were constructed at Ballynahatty. Due to chronological uncertainties and a possible hiatus in peat accumulation in the fen, the contemporary environment of the Ballynahatty timber circle complex (constructed and used ca. 3080-2490 cal. BC) and henge (dating to the third millennium cal. BC) cannot certainly be established. Nevertheless, the pollen record suggests that the landscape remained open through to the Bronze Age, implying a long continuity of human activity in the area. These findings support the idea that the Ballynahatty prehistoric complex was the product of a gradual and repeated restructuring of the ritual and ceremonial landscape whose significance continued to be recognised throughout the early prehistoric period.

Predatory nature of the littoral amphipod Echinogammarus marinus: gut content analysis and effects of alternative food and substrate heterogeneity

Interspecific interactions are major structuring forces in marine littoral communities; however, it is unclear which of these interactions are exhibited by many key-component species. Gut content analysis showed that the ubiquitous rocky/cobble shore amphipod Echinogammarus marinas, often ascribed as a mesograzer, consumes both algae and macroinvertebrates. Further, laboratory experiments showed that E. marinus is an active predator of such macroinvertebrates, killing and consuming the isopod Jaera nordmanni and the oligochaete Tubificoides benedii. Predatory impacts of E. marinus were not alleviated by the presence of alternative food in the form of alga discs. However, in the presence of prey, consumption of alga by E. marinus was significantly reduced. Further, survival of prey was significantly higher when substrate was provided, but predation remained significant and did not decline with further increases in substrate heterogeneity. We conclude that such amphipods can have pervasive predatory impacts on a range of species, with implications for community structure, diversity and functioning.

Co-existence of a pair of pelagic planktivorous coregonid fishes

Hypothesis: Ecological specialization facilitates co-existence of Coregonus spp. in Lake Stechlin. A difference in trophic ecology is the dominant means by which the species are ecologically segregated.

Comparative seasonal acclimatization of food and energy consumption in adjacent populations of common spiny mice (Acomys cahirinus)

Animals inhabiting environments with low productivity and food availability commonly have reduced energy demands and increased digestive efficiencies. The dry matter intake (DMI), apparent digestible dry matter (ADDM), digestible efficiency (DE) and digestible energy intake (DEI) of two populations of common spiny mouse Acomys cahirinus were compared during both winter and summer under conditions of simulated water stress. Mice were captured from the north- and south-facing slopes (NFS and SFS) of the same canyon that represent mesic and xeric habitats, respectively. Measured variables were also compared between F-1 mice that had been born to either NFS or SFS mice, and raised in the laboratory. SFS mice were able to assimilate energy more efficiently than NFS mice during the summer. By comparison, NFS mice were able to assimilate more energy during the winter. During winter, NFS mice assimilated more energy at low levels of water stress, whereas SFS mice assimilated more energy at higher levels. Differences were also apparent in F-1 mice. It is therefore suggested that local climatic conditions can impose physiological adaptations that are retained in succeeding generations, creating unique meta-populations.