• Energy Research

AbstractAlthough the role that Pleistocene glacial cycles have played in shaping the present biota of oceanic islands world‐wide has long been recognized, their geographical, biogeographical and ecological implications have not yet been fully incorporated within existing biogeographical models. Here we summarize the different types of impacts that glacial cycles may have had on oceanic islands, including cyclic changes in climate, shifts in marine currents and wind regimes and, especially, cycles of sea level change. The latter have affected geographical parameters such as island area, isolation and elevation. They have also influenced the configurations of archipelagos via island fusion and fission, and cycles of seamount emergence and submergence. We hypothesize that these sea level cycles have had significant impacts on the biogeographical processes shaping oceanic island biotas, influencing the rates and patterns of immigration and extinction and hence species richness. Here we provide a first step toward the development of a glacial‐sensitive model of island biogeography, representing the tentative temporal evolution of those biogeographical parameters during the last glacial cycle. From this reasoning we attempt to derive predictions regarding the imprint of sea level cycles on genetic, demographic or biogeographical patterns within remote island biotas.

Significance Assessing the ecological consequences of human settlement can help preserve island forests and their ecosystem services, but to understand the legacy of these interactions requires datasets that span centuries. We used paleoecological data (e.g. fossil pollen) to show that prehuman Holocene forests were dynamic in response to climatic changes, and that human colonization led to increased incidence of fire, soil erosion, and grazing impacts in the Canary Islands and Cabo Verde. Humans have driven compositional convergence within the thermophilous woodland zone of Cabo Verde but in the Canary Islands relictual fragments of laurel forests persist. Our long-term view highlights the legacy of past human impacts and which tree species to restore and conserve in thermophilous woodlands within these biodiversity hotspots.

Summary Garajonay National Park in La Gomera (Canary Islands) contains one of the largest remnant areas of a forest formation once widespread throughout Europe and North Africa. Here, we aim to address the long‐term dynamics (the last 9600 cal. years) of the monteverde forest (laurel forest and Morella‐Erica heath) located close to the summit of the National Park (1487 m a.s.l.) and determine past environmental and human impacts. We used palaeoecological (fossil pollen, microscopic and macroscopic charcoal) and multivariate ecological techniques to identify compositional change in the monteverde forest in relation to potential climatic and human influences, based on the analysis of a core site at 1250‐m elevation. The regional mid‐Holocene change towards drier conditions was matched in this system by a fairly rapid shift in representation of key forest elements, with declines in Canarian palm tree (Phoenix canariensis), Canarian willow (Salix canariensis) and certain laurel forest taxa and an increase in representation of the Morella–Erica woody heath. Charcoal data suggest that humans arrived on the island between about 3000 and 1800 years ago, a period of minimal vegetation change. Levels of burning over the last 800 years are among the lowest of the entire 9600 years. Synthesis. A rapid climatic‐induced shift of forest taxa occurred 5500 years ago, with a decrease in hygrophilous species in the pollen record. In contrast, we found no evidence of a significant response to human colonization. These findings support the idea that Garajonay National Park is protecting a truly ancient relict, comprising a largely natural rather than cultural legacy.

The form of the species richness–productivity relationship (SRPR) is both theoretically important and contentious. In an effort to distill general patterns, ecologists have undertaken meta‐analyses, within which each SRPR data set is first classified into one of five alternative forms: positive, humped (unimodal), negative, U‐shaped (unimodal), and no relationship. Herein, I first provide a critique of this approach, based on 68 plant data sets/studies used in three meta‐analyses published in Ecology. The meta‐analyses are shown to have resulted in highly divergent outcomes, inconsistent and often highly inappropriate classification of data sets, and the introduction and multiplication of errors from one meta‐analysis to the next. I therefore call on the ecological community at large to adopt a far more rigorous and critical attitude to the use of meta‐analysis. Second, I develop the argument that the literature on the SRPR continues to be bedeviled by a common failing to appreciate the fundamental importance of the scale of analysis, beginning with the confusion evident between concepts of grain, focus, and extent. I postulate that variation in the form of the SRPR at fine scales of analysis owes much to artifacts of the sampling regime adopted. An improved understanding may emerge from combining sampling theory with an understanding of the factors controlling the form of species abundance distributions and species accumulation curves.

AbstractConservation biogeography involves the application of biogeographical principles, theories, and analyses to problems regarding biodiversity conservation. The field was formally defined in 2005, and considerable research has been conducted in the ensuing 5 years.This editorial sets the context for 16 contributions in a special issue of Diversity and Distributions on developments and challenges in conservation biogeography. Papers are grouped into the following main themes: species distribution modelling; data requirements; approaches for assigning conservation priorities; approaches for integrating information from numerous disparate sources; special challenges involving invasive species; and the crucial issue of determining how elements of biodiversity are likely to respond to rapid climate change. One paper provides a synthesis of requirements for a robust conservation biogeography for freshwater ecosystems.Conservation biogeography is well poised to make a significant contribution to the process of providing policy makers with objectively formulated scenarios and options for the effective management of biodiversity. The editorial, and the papers in the special issue, deliberate on many of the exciting developments in play in the field, and the many complex challenges that lie ahead.

The Krakatau Islands, Indonesia, have provided an opportunity for ecologists to track primary succession from the ‘clean slate’ of 1883, through forest closure in the 1920s, to the contemporary period, in which successional changes take the form of alterations in composition and stature of forest stands rather than gross changes in ecosystem type. This paper reports on permanent forest plots established on the islands in 1989, and fully surveyed again in both 1992 and 1997. Since 1989, the plots have been subject to natural disturbance phenomena in the form of varying combinations of, for example, deposition of volcanic ejecta, landslides, lightning strikes, storm damage and drought. These effects have been concentrated between 1992 and 1997, during which the volcano Anak Krakatau has deposited ash on the islands of Sertung and Panjang, but not on Rakata. Data on stand responses are presented for growth rates (dbh (diameter at breast height, 1.3 m) increment), stem recruitment and mortality, biomass changes (partitioned into mortality, ingrowth and growth of established trees), and compositional shifts. The discussion focuses on evaluation of questions and successional models framed earlier in the programme. One general finding is that the stand dominants as of 1989 have tended to decline in number within the plots, generally through low levels of recruitment failing to balance rates of mortality. The effects of disturbance to the plots appear to be evident in terms of mortality and recruitment, dbh increment, and changes in biomass. The patterns of change in the eight plots are quite varied, such that relatively few generalizations are possible. The difficulties of establishing meaningful baseline rates for tree growth and stand biomass are discussed.