The evolution and ontogeny of the dentition of Myotragus balearicus Bate, 1909 (Artiodactyla, Caprinae): evidence from new fossil data

Myotragus balearicus Bate 1909 is an artiodactyl Caprinae endemic to the Balearic Islands (Spain), which became extinct more than 4000 years ago. It is characterized by a series of very unusual apomorphies acquired throughout its insular evolution, one of which is the presence of a single evergrowing incisor (with an open root) in each dentary. This incisor has been classically considered as I₁. The study of recendy discovered fossils of this species, which have been collected from the excavation of Holocene cave sediments in Cova Estreta (Pollenca, Mallorca) and in Cova des Moro (Manacor, Mallorca), together with the reexamination of materials belonging both to this species and to its ancestors, allowed us to study the ontogeny and evolution of the Myotragus dentition. The replacement of premolars differs only slighdy from the pattern recorded in ofiier bovids. Nevertheless, there are significant differences with other bovids regarding the incisiform series. Myotragus balearicus lacks secondary incisors. Through a neotenic process, which started during the Upper Pliocene, M. balearicus acquired a monophyodontic incisiform dentition, reducing the number of incisiforms to only one, identified as dl₂. The richness of the finds allows us to describe the different steps in this evolution. The only incisiform that appears to have been lost is dl_;l. The identification of the evergrowing incisor of M. balearicus as dl₂ reinforces its convergence with rodents postulated by Bate and there is discussion regarding homologies of incisors of rodents and lagomorphs.     

Morphology,ultrastructure and phylogenetic affinities of the single-island endemic Anthoceros cristatus Steph. (Ascension Island)

Oceanic islands, due to their geographical isolation, number, precisely defined boundaries and their geomorphological and climatic diversity, have provided enormous insights into speciation, dispersal, adaptive radiations and macroecological processes. One of the key components of these island studies is the role of single-island endemics (SIEs) as, in many instances, island biogeography models use the proportion of SIEs to infer evolutionary processes. It is, therefore, imperative to undertake critical taxonomic revisions to evaluate SIEs because changes in the number of SIEs have a key impact on downstream biogeographic analyses. We revise the special case of a putative SIE Anthoceros cristatus on Ascension Island using light and electron microscopy, as well phylogenomic tools. A. cristatus lies within the A. agrestis/A. punctatus complex but differs from the sister species A. agrestis and A. punctatus in spore morphology and gametophytic lamellae fringed with caducous marginal cells. The present confirmation, from both molecules and morphology, of the SIE status of Anthoceros cristatus and its restricted distribution on the Island makes the preservation of its habitat a conservation priority. Ascension Island is the tip of an undersea volcano that is thought to have emerged from the ocean 1 million years ago with an area of approximately 91?km², with Green Mountain as the highest elevation (～859?m a.s.l.). Ascension has a relative low bryophyte species diversity of 87 spp but this includes 12 endemics (～14%); a much higher level of endemism than on the far more speciose Macaronesian Islands.     

Islands as biological substrates: Continental

Aim

Describe the main geo‐physical features of the various sorts of marine islands that are associated with the continents and consider how the ontogenetic pathways of each landmass type might have shaped the hosted biotas.

Location

Global.

Methods

Review of the literature that underpins understanding of the “continental” marine islands, particularly those publications with biological, geological, geophysical, oceanographical and palaeoceanographical foci.

Results

Based on their geo‐physical settings, islands with continental basements/close connections to the continents can be assigned to one of nine categories: shelf, shelf volcano, orogenic margin, continental arc, continental fore‐arc, rifted arc‐raft, isolated raft atoll, isolated block and micro‐continental terrane. As each functions in a distinctive manner, this must have strongly imprinted the native biotas.

Main conclusions

“Continental” marine islands can be allocated to one of nine groups based on their respective geo‐physical locations. When geological time is considered, then the unique histories of each insular landmass type will have played a critical role in moulding the land‐locked faunal assemblages that have amassed and evolved atop them. Researchers investigating insular biotas, particularly those exploring biodiversity growth, may wish to accommodate these insights.     

How to define nativeness in vagile organisms: lessons from the cosmopolitan moss Bryum argenteum on the island of Tenerife (Canary Islands)

The distinction between native and introduced biotas presents unique challenges that culminate in organisms with high long‐distance dispersal capacities in a rapidly changing world. Bryophytes, in particular, exhibit large distribution ranges, and some species can truly be qualified as cosmopolitan. Cosmopolitan species, however, typically occur in disturbed environments, raising the question of their nativeness throughout their range. Here, we employ genetic data to address the question of the origin of the cosmopolitan, weedy moss Bryum argenteum on the island of Tenerife. The genetic diversity of B. argenteum on Tenerife was comparable to that found in continental areas due to recurrent colonisation events, erasing any signature of a bottleneck that would be expected in the case of a recent colonisation event. The molecular dating analyses indicated that the first colonisation of the island took place more than 100,000 years ago, i.e. well before the first human settlements. Furthermore, the significant signal for isolation‐by‐distance found in B. argenteum within Tenerife points to the substantial role of genetic drift in establishing the observed patterns of genetic variation. Together, the results support the hypothesis that B. argenteum is native on Tenerife; although the existence of haplotypes shared between Tenerife and continental areas suggests that more recent, potentially man‐mediated introduction also took place. While defining nativeness in organisms that are not deliberately introduced, and wherein the fossil record is extremely scarce, is an exceedingly challenging task, our results suggest that population genetic analyses can represent a useful tool to help distinguish native from alien populations.     

Oceanic island biogeography through the lens of the general dynamic model: assessment and prospect

The general dynamic model of oceanic island biogeography (GDM) has added a new dimension to theoretical island biogeography in recognizing that geological processes are key drivers of the evolutionary processes of diversification and extinction within remote islands. It provides a dynamic and essentially non‐equilibrium framework generating novel predictions for emergent diversity properties of oceanic islands and archipelagos. Its publication in 2008 coincided with, and spurred on, renewed attention to the dynamics of remote islands. We review progress, both in testing the GDM's predictions and in developing and enhancing ecological–evolutionary understanding of oceanic island systems through the lens of the GDM. In particular, we focus on four main themes: (i) macroecological tests using a space‐for‐time rationale; (ii) extensions of theory to islands following different patterns of ontogeny; (iii) the implications of GDM dynamics for lineage diversification and trait evolution; and (iv) the potential for downscaling GDM dynamics to local‐scale ecological patterns and processes within islands. We also consider the implications of the GDM for understanding patterns of non‐native species diversity. We demonstrate the vitality of the field of island biogeography by identifying a range of potentially productive lines for future research.     

Hello New Zealand

Islands of the Pacific Ocean have long fascinated evolutionists. Oceanic islands, generally the products of volcanic activity, provide natural experiments as biological populations are well delimited and the age of islands can be determined using radiometric dating. 'Continental islands', including New Caledonia and New Zealand, provide equally valuable opportunities for evolutionary study. For students of New Zealand biogeography, the peculiar composition of the biota coupled with a limited interpretation of geology has resulted in the widespread acceptance that the flora and fauna is primarily ancient and of vicariant Gondwanan origin. There is increasing evidence from molecular data that much of this biodiversity is the product of evolution following relatively recent colonization. Such data have prompted biologists to consider geological information on New Zealand in more detail. At the heart of the issue is the question of whether modern New Zealand has a terrestrial link through time with the continent Zealandia that split from Gondwanaland some 80 Ma. Zealandia, which includes New Caledonia, Lord Howe Island and several of the subantarctic islands, is now largely submerged, and New Zealand's present terrestrial existence is the product of tectonic activity initiated around 26 Ma. We argue that for the purposes of biogeographical interpretation, New Zealand can be treated as an oceanic island.     

Insularity effects on bird immune parameters: A comparison between island and mainland populations in West Africa

Oceanic islands share several environmental characteristics that have been shown to drive convergent evolutionary changes in island organisms. One change that is often assumed but has seldom been examined is the evolution of weaker immune systems in island species. The reduction in species richness on islands is expected to lead to a reduced parasite pressure and, given that immune function is costly, island animals should show a reduced immune response. However, alternative hypotheses exist; for example, the slower pace of life on islands could favor the reorganization of the immune system components (innate vs. acquired immunity) on islands. Thus far, few island species have been studied and no general patterns have emerged. Here, we compared two immune parameters of birds from São Tomé and Príncipe islands to those of their close relatives at similar latitudes on the mainland (Gabon, West Africa). On islands, the acquired humoral component (total immunoglobulins) was lower for most species, whereas no clear pattern was detected for the innate component (haptoglobin levels). These different responses did not seem to arise from a reorganization of the two immune components, as both total immunoglobulins and haptoglobin levels were positively associated. This work adds to the few empirical studies conducted so far which suggest that changes in immune parameters in response to insularity are not as straightforward as initially thought.     

千岛湖片段化栖息地地栖哺乳动物的红外相机监测及最小监测时长

作为典型的陆桥岛屿, 千岛湖成为检验栖息地片段化理论的自然研究平台。2011年5月1日至2014年3月31日, 我们在千岛湖32个岛屿和1个大陆对照样点布设了60台红外相机, 对千岛湖体型较大的地栖兽类及其最小监测时长进行了监测和研究。在27,798个相机日的监测中, 共获得动物影像照片23,639张, 照片清晰、可进行物种鉴定的有2,414张, 占照片总数的10.2%; 其中体型较大的地栖兽类独立照片988张, 识别为9个物种: 穿山甲(Manis pentadactyla)、黄麂(Muntiacus reevesi)、野猪(Sus scrofa)、华南兔(Lepus sinensis)、马来豪猪(Hystrix brachyuran)、猪獾(Arctonyx collaris)、鼬獾(Melogale moschata)、花面狸(Paguma larvata)和豹猫(Prionailurus bengalensis), 平均独立照片拍摄率为40.9%。种-面积曲线研究表明, 岛屿上的地栖兽类物种丰富度随着岛屿面积的增大而增大, 曲线的z值为0.27。大岛(>10 ha)中, 最小监测时长随面积增加而增加, 而小岛没有明显趋势; 最小监测时长随隔离度增加而减小, 但关系不显著(d.f. = 20, F = 3.067, P = 0.095), 表明建湖后栖息地的片段化与岛屿化导致了一些对面积或栖息地较为敏感的大型兽类在小岛屿上的局部灭绝。因此, 我们建议对于面积较大的片段化栖息地, 红外相机应保证较长的最小监测时长, 而面积较小的片段化栖息地在监测中应根据隔离度、基质性质、物种种类适时调整调查强度, 以完整反映当地物种实际情况。     

Implications of reef ecosystem change for the stability and maintenance of coral reef islands

Coral reef islands are among the most vulnerable environments on Earth to climate change because they are low lying and largely constructed from unconsolidated sediments that can be readily reworked by waves and currents. These sediments derive entirely from surrounding coral reef and reef flat environments and are thus highly sensitive to ecological transitions that may modify reef community composition and productivity. How such modifications – driven by anthropogenic disturbances and on‐going and projected climatic and environmental change – will impact reef island sediment supply and geomorphic stability remains a critical but poorly resolved question. Here, we review the unique ecological–geomorphological linkages that underpin this question and, using different scenarios of environmental change for which reef sediment production responses can be projected, explore the likely resilience of different island types. In general, sand‐dominated islands are likely to be less resilient than those dominated by rubble grade material. However, because different islands typically have different dominant sediment constituents (usually either coral, benthic foraminifera or Halimeda) and because these respond differently to individual ecological disturbances, island resilience is likely to be highly variable. Islands composed of coral sands are likely to undergo major morphological change under most near‐future ecological change scenarios, while those dominated by Halimeda may be more resilient. Islands composed predominantly of benthic foraminifera (a common state through the Pacific region) are likely to exhibit varying degrees of resilience depending upon the precise combination of ecological disturbances faced. The study demonstrates the critical need for further research bridging the ecological–geomorphological divide to understand: (1) sediment production responses to different ecological and environmental change scenarios; and (2) dependant landform vulnerability.     

Historical perspectives on human-assisted biological invasions

Of all the things we have done to the Earth so far, which one is likely to make the most indelible mark? I have been posing this question to students and colleagues for some time, and usually receive one of three reasonable replies: habitat destruction, human overpopulation, or global climate change. Yet as bad as all these maladies are, they are, to some extent, reversible on time scales to which we can relate. The remedies for these problems, despite mammoth cultural and economic obstacles, can be visualized generally in terms of technology and scientific theory. Only the will is lacking. On longer geological and evolutionary time scales, most such human impacts, if corrected soon, would be mere blips, perturbations of the ecosphere that would leave only a few detectable traces in the fossil record a million years hence.     

Gene flow and species cohesion following the spread of Schiedea globosa (Caryophyllaceae) across the Hawaiian Islands

Island radiations are often regarded as natural laboratories that allow us to study evolution in action. The genus Schiedea (Caryophyllaceae) is one of the largest radiations of angiosperms in the Hawaiian Islands, and Schiedea globosa is one of the few species in the genus to be found on more than one of the main islands. DNA sequences from nineteen nuclear and three chloroplast regions show a pattern of colonization from older to younger islands (west to east), with a concomitant decrease in genetic diversity eastwards (π=0.53% for O'ahu, 0.43% for Moloka'i and 0.36% for Maui). While polymorphisms in the maternally inherited chloroplast have become fixed on different islands (F(ST)=0.804), significant gene flow between islands is inferred for the nuclear genome (F(ST)=0.270). This gene flow appears to be uneven, with most gene flow outwards from the central island. The extent of inter-island gene flow through wind pollination was assessed in an isolation-migration framework; the inferred rate, c. 1 migrant per generation, may be sufficient to prevent divergence of S. globosa populations and ensure cohesion of the species following the colonization of new islands.     

Persistence, extinction and different species pools within the flora of lake islands in western Ireland

The vascular flora on twenty-nine lake islands in Lough Corrib, western Ireland was surveyed in 1992–93. Thirteen of these islands had been surveyed by the author in 1974 (Roden, 1979). Data on species–area curves and species turnover between 1974 and 1992 are presented. Species numbers on each island did not change greatly in the 18-year interval and extinctions were most common on smaller islands. It is known that six of the islands surveyed are less than 150 years old and their flora must have immigrated over open water during that period. It is shown that this group of species has a different log species/log area regression than the remaining flora, with a much shallower slope (low Z value). The proportion of less widespread species was greatest on islands nearest to the mainland. The implication of different slopes in different species groups and the restriction of turnover to rare species is discussed with reference to the island Theory of Biogeography.     

Cryptic species,gene recombination and hybridization in the genus Spiraeanthemum (Cunoniaceae) from New Caledonia

The Oceanian plant genus Spiraeanthemum (Cunoniaceae) has a centre of diversity in New Caledonia, where it is represented by seven species. Its diversification was investigated using two low‐copy nuclear genes, ncpGS and GapC, and phylogenetic analyses were based on maximum parsimony, maximum likelihood and recombination networks. We detected several cases of gene recombination in both datasets, and these have obscured the history within the genus. For S. ellipticum and S. pubescens, accessions from southern populations on ultramafic soils were genetically distinct from accessions from northern populations on non‐ultramafic soils. Given that no obvious morphological characters distinguish northern and southern populations in either taxon, both may be considered as examples of cryptic species. Incongruence between gene trees and species' delimitation may be explained by the parallel evolution of similar morphology, differential lineage sorting leading to differential fixation of alleles or different introgression patterns in the north and south leading to allele displacement. In New Caledonia, some species with broad ecological preferences may thus be artificial concepts. This suggests that they should be treated more critically in monographs and that the species' richness of the New Caledonian flora may be underestimated. Problems associated with the typification of S. ellipticum and evidence of hybridization events in the history of Spiraeanthemum are also discussed. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 161 , 137–152.     

基于Landsat-8影像的沿海城市公园冷岛效应——以厦门为例

城市公园主要由水体和绿色植被等景观构成,其形成的公园冷岛(Park cool island,PCI)已成为减缓城市热岛效应的重要途径之一。采用景感生态学中的景感营造理念规划设计城市公园或优化公园空间结构有助于增强公园冷岛效应,进一步改善局地城市热环境。选择沿海城市——厦门市为研究对象,基于2013年8月的Landsat-8 OLI/TIRS遥感影像和Google Earth高分影像数据,首先提取了研究区15个公园的土地利用信息,采用改进的地表温度单通道算法,获取了城市公园地表温度数据,并采用缓冲区分析、景观格局指数和多元统计等方法定量分析公园内部平均地表温度、城市公园冷岛强度(即降温幅度)、公园冷岛影响距离(即对周边区域的降温范围)三者的主要影响因子,并利用景感生态学原理初步剖析了城市公园景感营造的原则。结果显示:(1)公园面积和公园建设用地面积是影响公园平均温度的关键因子(R²=0.915),这两个因子与公园平均温度均呈显著非线性相关;公园面积存在阈值55 hm²左右;(2)公园冷岛PCI强度由公园绿地面积、公园建筑面积和面积-周长形状指数...     

Of mice and mammoths: generality and antiquity of the island rule

Aim

We assessed the generality of the island rule in a database comprising 1593 populations of insular mammals (439 species, including 63 species of fossil mammals), and tested whether observed patterns differed among taxonomic and functional groups.

Location

Islands world‐wide.

Methods

We measured museum specimens (fossil mammals) and reviewed the literature to compile a database of insular animal body size (S_i = mean mass of individuals from an insular population divided by that of individuals from an ancestral or mainland population, M). We used linear regressions to investigate the relationship between S_i and M, and ANCOVA to compare trends among taxonomic and functional groups.

Results

S_i was significantly and negatively related to the mass of the ancestral or mainland population across all mammals and within all orders of extant mammals analysed, and across palaeo‐insular (considered separately) mammals as well. Insular body size was significantly smaller for bats and insectivores than for the other orders studied here, but significantly larger for mammals that utilized aquatic prey than for those restricted to terrestrial prey.

Main conclusions

The island rule appears to be a pervasive pattern, exhibited by mammals from a broad range of orders, functional groups and time periods. There remains, however, much scatter about the general trend; this residual variation may be highly informative as it appears consistent with differences among species, islands and environmental characteristics hypothesized to influence body size evolution in general. The more pronounced gigantism and dwarfism of palaeo‐insular mammals, in particular, is consistent with a hypothesis that emphasizes the importance of ecological interactions (time in isolation from mammalian predators and competitors was 0.1 to > 1.0 Myr for palaeo‐insular mammals, but < 0.01 Myr for extant populations of insular mammals). While ecological displacement may be a major force driving diversification in body size in high‐diversity biotas, ecological release in species‐poor biotas often results in the convergence of insular mammals on the size of intermediate but absent species.