Maintenance of Genetic Diversity: Challenges for Management of Marine Diversity

There are three general classes of threat to biodiversity at the gene level: 1) extinction, which result in complete and irreversible loss of genes; 2) hybridization, which may cause re-arrangement of co-adapted genes and loss of adaptability to local conditions, and 3) reduction of genetic variability within populations. While extinction avoidance is a fundamental management objective and hybridization can usually be dismissed in marine populations, the reduction of genetic variability within populations is a plausible threat and can occur in two ways. First, a decrease in population size may result in inbreeding. Normally, marine fish have very large population sizes, and commercial extinction is likely to occur long before populations are reduced to the level required for losses of genetic diversity due to inbreeding. However, when populations are very severely over-fished to small numbers, concerns associated with small population sizes and disruptions of migration between populations may become prominent. In particular, undetected populations within management units may be fished to this level before the situation is properly evaluated and remedied. Second, a reduction of genetic variability within populations may occur in a directed way, due to, e.g., selective fishing. Fishing is expected to generate selection on life history traits such as age and size at maturation; changes in life history traits influence the dynamics of fish populations, energy flows in the ecosystem, and ultimately, sustainable yield. We discuss management objectives designed to ameliorate genetic complications associated with small population size and fisheries-induced selection, and outline a management approach that may be useful when developing advice for maintaining genetic diversity

Science, biodiversity and Australian management of marine ecosystems

The United Nations Convention on Law of the Sea (UNCLOS) (United Nations 1982) came into effect in 1994. Signatory nations have substantial management obligations for conservation of marine natural resource and ecosystems. In this paper we discuss the challenges of defining and monitoring biodiversity at scales required for management of marine ecosystems. Australia\u27s area of immediate responsibility under UNCLOS covers an area of 11 million sq km with further linked responsibilities for an estimated area of 5.1 million sq km of continental shelf. This presents substantial data challenges for development and implementation of management. Acoustic seabed mapping is providing substantial information on seabed surface geology and topography and provides a surrogate basis for describing benthic habitat and seabed communities that have critical roles in marine food chains. The development of the Integrated Marine and Coastal Regionalisation of Australia (IMCRA 4.0, 2006) has provided a basis for planning marine biodiversity and resource management but the biological habitat interpretation of geological data is based very largely on demersal fish data. It is recognised in IMCRA 4.0 (2006) that revision and refinement of regionalisation requires further work in the areas of data coverage, ecosystem understanding and ecosystem surrogates and conceptual classification models. In this paper we discuss Australian experience highlighting problems and issues of relevance for scientifically based management of marine natural resource and ecosystems elsewhere in the world

Role of low intensity environmental disturbance in structuring the earliest (Ediacaran) macrobenthic tiered communities

Rangeomorphs were important components of Ediacaran macrobenthic ecosystems, yet their biology and ecology remain poorly constrained. They formed high-density, tiered communities that were subjected to intermittent burial events, the largest of which killed entire communities. Abundant thin event beds in the Ediacaran succession of Charnwood Forest indicate the additional, frequent impact of minor obrution events. The type surface of Charniamasoni is immediately underlain by one such lamina (a tuff) and preserves a distinctly bimodal population. It is dominated by Charnia fronds that are of smaller or comparable length to the holotype (19.4 cm), but also includes notably larger specimens (N45 cm) that would traditionally have been assigned to Charnia grandis. Multiple morphological- and morphometric parameters (length, width, spacing of primary branches) demonstrate that these are indistinguishable from the holotype of C. masoni, affirming the synonymy of the two taxa. Nevertheless, these outsized individuals are distinguished by their proportionally fewer primary branches per unit length. Taphonomic evidence indicates that they were survivors of an incumbent population, the rest of which was culled by a minor ashfall.We suggest that this temporary reduction in competition from neighbours allowed the survivors to grow larger and thereby gain access to a greater proportion of the water column. As the community recovered, their large sizewould have continued to provide themwith an advantage, divorcing them from the density-dependent competition seen in the new understory. The interlude between cohorts implies that newrecruitswere substrate-sensitive, presumably awaiting re-establishment of the biomat. Sub-lethal disturbance events thus played a significant role in structuring Ediacaran communities, and help explain the observed bed-by-bed variability. Taken as a whole, the growth trajectory of C. masoni resembles that of extant organismswith indeterminate growth programmes and no genetically-controlled upper size limit.PRW and CGK were supported by NERC grant NE/I005927/1. We thank our colleagues Mark Dean, Sue Martin, Louise Neep, Scott Renshaw and Paul Shepherd for assistance with moulding and casting; Paul Witney and Simon Harris for photography; and Henry Holbrook for drafting Figs. 1 and 2. We gratefully acknowledge the help in facilitating site access given by Natural England, the Mistaken Point Ecological Reserve (Parks and Natural Areas Division, Government of Newfoundland and Labrador) and landowners in Charnwood Forest. We enjoyed useful discussions with Alex Liu and Helen Boynton, and Mark Woods, Guy Harrington, Lidya Tarhan and two anonymous referees are thanked for their constructive comments on the manuscript.This is the final published version. It first appeared at http://www.sciencedirect.com/science/article/pii/S0031018215001649

Remarkable insights into the paleoecology of the Avalonian Ediacaran macrobiota

Ediacaran macrofossils from the Avalon Terrane (primarily eastern Newfoundland and the central UK) record some of the earliest large and complex multicellular organisms on Earth. Perhaps the greatest unknown regarding these fossils is their relevance to the early evolutionary history of the Kingdom Animalia. In recent years, new data and discoveries have revealed insights into Ediacaran paleobiology, taxonomic relationships, paleoecology and taphonomy, significantly refining our understanding of Avalonian ecosystems. Here, we summarise recent observational and quantitative studies, and their bearing on the current understanding of Avalonian benthic marine ecosystems. A review of existing knowledge of the biological composition of Avalonian marine assemblages demonstrates that they record densely-populated ecosystems inhabited by a diverse range of organisms, likely representing multiple biological Kingdoms. Appreciation of this diversity, and of the complexities it introduces to paleoecological studies, is vital when considering the relationship between macroevolution and contemporaneous climatic, tectonic and geochemical events. We then summarise current understanding of Avalonian paleoecology. Studies into locomotion, reproduction, feeding strategies, and community structure and succession reveal that these ecosystems were considerably different to Phanerozoic settings. Furthermore, we suggest that Avalonian ecosystems witnessed the appearance of novel nutrient sources, offering new opportunities and niches for benthic organisms. The suggestion that the numerically dominant rangeomorphs were osmotrophic is reviewed and appraised in light of geochemical, morphological, and biological information. Finally, the use of modern ecological metrics in the study of Ediacaran fossil assemblages is assessed. Concerns regarding the interpretation of paleoecological data are outlined in light of current taphonomic and sedimentological understanding, and these cast doubt on previous suggestions that the Avalonian assemblages were largely composed of metazoans. Nevertheless, we emphasise that if treated with necessary caution, paleoecological data can play a significant role in assisting efforts to determine the biological affinities of late Ediacaran macroscopic organisms.Thanks are extended to the editors of Gondwana Research, T. Horscroft and M. Santosh, for inviting this review, and for their patience whilst we completed it. The Parks and Natural Areas Division, Department of Environment and Conservation, Government of Newfoundland and Labrador provided permits to conduct research within the Mistaken Point Ecological Reserve between 2008–2013, whilst the Department of Tourism, Culture and Recreation provided permits for paleontological research in other parts of the Province from 2012–2013. The support of the Portugal Cove South Visitor Center interpreters during our field research was greatly appreciated. This work has been supported by the Natural Environment Research Council [grant numbers NE/I005927/1 to CGK and NE/G523539/1 to EGM]; a Henslow Junior Research Fellowship from Cambridge Philosophical Society to AGL; and the National Geographic Global Exploration Fund [GEFNE 22-11 to AGL]. Field assistance from J. Matthews, J. Stewart, D. Collins, and T. Hearing has been invaluable, and we have enjoyed fruitful discussions on this topic with N. Butterfield, D. McIlroy, J. Hoyal Cuthill, M. Brasier, S. Conway Morris and P. Wilby. The work and support of past and current workers in this field is gratefully acknowledged. B. MacGabhann and one anonymous reviewer are thanked for providing detailed comments that have strengthened this manuscript, whilst S. Jensen and M. Friedman provided helpful feedback on parts of this manuscript assessed as a chapter of AGL's thesis.This is the final published version of an article that was originally published in Gondwana Research, Available online 4 December 2014, doi:10.1016/j.gr.2014.11.00

Of time and taphonomy: preservation in the Ediacaran

The late Neoproterozoic witnessed a revolution in the history of life: the transition from a microbial world to the one we know today. The enigmatic organisms of the Ediacaran hold the key to understanding the early evolution of metazoans and their ecology, and thus the basis of Phanerozoic life. Crucial to interpreting the information they divulge is a thorough understanding of their taphonomy: of what is preserved andhow it is preserved, and also of what is not preserved. Fortunately, this Period is also recognized for its abundance of soft-tissue preservation, which is viewed through a wide variety of taphonomic windows. Some of these, such as pyritization and carbonaceous compression, are also present throughout the Phanerozoic, but the abundance and variety of moldic preservation of body fossils in siliclastic settings is unique to the Ediacaran. In rare cases, one organism is preserved in several preservational styles which, in conjunction with our increased understanding of the taphonomic processes involved in each style, allow us to more confidently interpret aspects of the biology and ecology of the organisms preserved. Several groundbreaking advances in this field have been made since the 1990s, and have paved the way for increasingly thorough analyses and elegant interpretations

The utility of height for the Ediacaran organisms of Mistaken Point.

Ediacaran fossil communities consist of the oldest macroscopic eukaryotic organisms. Increased size (height) is hypothesized to be driven by competition for water column resources, leading to vertical/epifaunal tiering and morphological innovations such as stems. Using spatial analyses, we find no correlation between tiering and resource competition, and that stemmed organisms are not tiered. Instead, we find that height is correlated with greater offspring dispersal, demonstrating the importance of colonization potential over resource competition.Gibbs Travelling Fellowship from Newnham College, University of Cambridge Henslow Research Fellowship, Cambridge Philosophical Society

Modularity and overcompensatory growth in Ediacaran rangeomorphs demonstrate early adaptations for coping with environmental pressures

The first known diverse, complex, macroscopic benthic marine ecosystems (late Ediacaran, ca. 571-541 Ma) were dominated by the Rangeomorpha, an enigmatic group of extinct frondose eukaryotes that are candidate early metazoans[1,2]. The group is characterised by a self-similar branching architecture that was likely optimised for exchange, but nearly every other aspect of their biology is contentious[2–4]. We report locally-enhanced, aberrant growth (“eccentric branching”) in a stalked, multifoliate rangeomorph – Hylaecullulus fordi n. gen., n. sp. – from Charnwood Forest (UK), confirming the presence of true biological modularity within the group. Random branches achieve unusually large proportions and mimic the architecture of their parent branch, rather than that of their neighbours (the norm). Their locations indicate exceptional growth at existing loci, rather than insertion at new sites. Analogous over-compensatory branching in extant modular organisms requires the capacity to orchestrate growth at specific sites, and occurs most frequently in response to damage or environmental stress, allowing regeneration towards optimum morphology[e.g. 5–7]. Its presence in rangeomorphs indicates a hitherto unappreciated level of control to their growth plan, a previously unrecognised form of morphological plasticity within the group, and an ability to actively respond to external physical stimuli. The trait would have afforded rangeomorphs resilience to fouling and abrasion, partially accounting for their wide environmental tolerance, and may have pre-adapted them to withstand predation, weakening this argument for their extinction. Our findings highlight that multiple, phylogenetically disparate, clades first achieved large size through modularity

Mapping benthic ecological diversity and interactions with bottom-contact fishing on the Flemish Cap (northwest Atlantic)

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