• Eutrophication erodes inter-basin variation in macrophytes and co-occurring invertebrates in a shallow lake: combining ecology and palaeoecology

      Salgado, J; Sayer, CD; Brooks, SJ; Davidson, TA; Okamura, B (Springer, 2017-03-13)
      Aquatic biodiversity is commonly linked with environmental variation in lake networks, but less is known about how local factors may influence within-lake biological heterogeneity. Using a combined ecological and multi-proxy palaeoecological approach we investigated long-term changes in the pathways and processes that underlie eutrophication and water depth effects on lake macrophyte and invertebrate communities across three basins in a shallow lake—Castle Lough, Northern Ireland, UK. Contemporary data allow us to assess how macrophyte assemblages vary in composition and heterogeneity according to basin-specific factors (e.g. variation in water depth), while palaeoecological data (macrophytes and co-occurring invertebrates) enable us to infer basin-specific impacts and susceptibilities to nutrient-enrichment. Results indicate that variability in water depth promotes assemblage variation amongst the lake basins, stimulating within-lake macrophyte assemblage heterogeneity and hence higher lake biodiversity. The palaeo-data indicate that eutrophication has acted as a strong homogenising agent of macrophyte and invertebrate diversities and abundances over time at the whole-lake scale. This novel finding strongly suggests that, as eutrophication advances, the influence of water depth on community heterogeneity is gradually eroded and that ultimately a limited set of eutrophication-tolerant species will become homogeneously distributed across the entire lake.
    • Insights into the abundance and diversity of abyssal megafauna in a polymetallic-nodule region in the eastern Clarion-Clipperton Zone

      Amon, Diva; Ziegler, AF; Dahlgren, TG; Glover, AG; Goineau, A; Gooday, AJ; Wiklund, H; Smith, CR (Springer, 2016-07-29)
      There is growing interest in mining polymetallic nodules in the abyssal Clarion-Clipperton Zone (CCZ) in the Pacific. Nonetheless, benthic communities in this region remain poorly known. The ABYSSLINE Project is conducting benthic biological baseline surveys for the UK Seabed Resources Ltd. exploration contract area (UK-1) in the CCZ. Using a Remotely Operated Vehicle, we surveyed megafauna at four sites within a 900 km2 stratum in the UK-1 contract area, and at a site ~250 km east of the UK-1 area, allowing us to make the first estimates of abundance and diversity. We distinguished 170 morphotypes within the UK-1 contract area but species-richness estimators suggest this could be as high as 229. Megafaunal abundance averaged 1.48 ind. m−2. Seven of 12 collected metazoan species were new to science, and four belonged to new genera. Approximately half of the morphotypes occurred only on polymetallic nodules. There were weak, but statistically significant, positive correlations between megafaunal and nodule abundance. Eastern-CCZ megafaunal diversity is high relative to two abyssal datasets from other regions, however comparisons with CCZ and DISCOL datasets are problematic given the lack of standardised methods and taxonomy. We postulate that CCZ megafaunal diversity is driven in part by habitat heterogeneity.
    • Local extinctions of insular avifauna on the most remote inhabited island in the world

      Bond, AL; Carlson, CJ; Burgio, KR (Springer, 2018-08-13)
      The overwhelming majority of avian extinctions have occurred on islands, where introduced predators, habitat loss, disease, and human persecution have resulted in the loss of over 160 species in the last 500 years. Understanding the timing and causes of these historical extinctions can be beneficial to identifying and preventing contemporary biodiversity loss, as well as understanding the nature of island ecosystems. Tristan da Cunha (henceforth “Tristan”), the most remote inhabited island in the world, has lost three species from the main island since permanent human settlement in 1811—the Tristan Moorhen (Gallinula nesiotis), Inaccessible Finch (Nesospiza acunhae acunhae), and Tristan Albatross (Diomedea dabbenena). We used recently developed Bayesian methods, and sightings of mixed certainty compiled from historical documents, to estimate the extinction date of these three species from Tristan based on specimens. We estimate that all three species were likely extirpated from Tristan between 1869 and 1880 following a period of significant habitat alteration and human overexploitation, and only the albatross had a high probability of persistence when Black Rats (Rattus rattus) arrived in 1882, the previously assumed cause of extinction for all three species. Better estimates of extinction dates are essential for understanding the causes of historical biodiversity loss, and the combination of historical ecology with modern statistical methods has given us novel insights into the timing and therefore the causes of extinctions on one of the most isolated islands in the world.
    • Patterns of magnesium content in Arctic bryozoan skeletons along a depth gradient

      Taylor, PD; Borszcz, Tomasz; Kuklin´ski, Piotr (Springer, 2012-10-14)
      A growing body of evidence suggests that ocean acidification acting synergistically with ocean warming alters carbonate biomineralization in a variety of marine biota. Magnesium often substitutes for Ca in the calcite skeletons of marine invertebrates, increasing their solubility. The spatio-environmental distribution of Mg in marine invertebrates has seldom been studied, despite its importance for assessing vulnerabilities to ocean acidification. Because pH decreases with water depth, it is predicted that levels of Mg in calcite skeletons should also decrease to counteract dissolution. Such a pattern has been suggested by evidence from echinoderms. Data on magnesium content and depth in Arctic bryozoans (52 species, 103 individuals, 150 samples) are here used to test this prediction, aided by comparison with six conceptual models explaining all possible scenarios. Analyses were based on a uniform dataset spanning more than 200 m of coastal water depth. No significant relationship was found between depth and Mg content; indeed, the highest Mg content among the analyzed taxa (8.7 % mol MgCO3) was recorded from the deepest settings (>200 m). Our findings contrast with previously published results from echinoderms in which Mg was found to decrease with depth. The bryozoan results suggest that ocean acidification may have less impact on the studied bryozoans than is generally assumed. In the broad context, our study exemplifies quantitative testing of spatial patterns of skeletal geochemistry for predicting the biological effects of environmental change in the oceans.
    • Perforocycloides nathalieae new genus and species, an unusual Silurian cyclocystoid (Echinodermata) from Anticosti Island, Québec, Canada

      Graham, M; Ewin, TAM; Reich, Mike; Cournoyer, ME; Klug, C (Springer, 2019-08-22)
      Cyclocystoids are a poorly known, rare, extinct class of bi-facially flattened, disc shaped echinoderms, ranging from the Middle Ordovician to the Early Carboniferous. Articulated cyclocystoids are relatively common in the Ordovician but are rarer in younger strata. Here we describe Perforocycloides nathaliae new genus and species, from the early Silurian of Anticosti Island, Québec, Canada, the first articulated cyclocystoid from the Silurian of North America. This taxon is distinguished from other cyclocystoids by the number of variably sized marginal ossicles, the lack of interseptal plates, and the novelty of pores located in the distal part of the sutures between adjacent marginals on the dorsal surface. These dorsal intermarginal sutural pores led to canals which penetrated the contiguous area of the lateral surface of the marginals and emerged on the ventral surface between the cupules of adjacent marginals. These dorsal intermarginal sutural pores/canals appear to be unique to Perforocycloides and whilst their function is speculative, they provided some form of communication between the dorsal disc and the distal side of the ventral marginals/cupules. Perforocycloides most closely resembles the Ordovician–Silurian genus Zygocycloides, suggesting that this genus may have diversified more widely during the Silurian than previously reported. A review of global Silurian cyclocystoid distribution suggests taxa were geographically confined and that greatest diversity appears to have been located within Baltica. However, it also demonstrates our current limited knowledge. No specimens have been recorded from Gondwana (e.g. Africa, Australia, South America), Siberia, and North and South China, nor are any specimens known confidently anywhere from Přidolí strata.
    • The Tomato (Solanum lycopersicum L., Solanaceae) and Its Botanical Relatives

      Knapp, S; Peralta, IE; Causse, M; Giovannoni, J; Bouzayen, M; Zouine, M (Springer, 2016-11-24)
      The cultivated tomato, Solanum lycopersicum L., is a member of the small section Lycopersicon along with its 12 wild relatives. An additional four species from sections Juglandifolia and Lycopersicoides are traditionally considered as tomato wild relatives. These species are all endemic to South America, but the cultivated tomato itself has achieved worldwide distribution with the help of human populations. Tomato and its wild relatives are part of a larger monophyletic group (the Potato clade) that also contains the potatoes and their wild relatives. Here we review the taxonomic and phylogenetic history, relationships and species-level taxonomy of the cultivated tomato and its wild relatives, and highlight important studies of diversity that remain to be undertaken in the group, especially in light of global environmental and climatic change.