scholarly journals Developmental mode influences diversification in ascidians

2013 ◽  
Vol 9 (3) ◽  
pp. 20130068 ◽  
Author(s):  
Max E. Maliska ◽  
Matthew W. Pennell ◽  
Billie J. Swalla
Keyword(s):  
Larval Development ◽  
Posterior Distribution ◽  
Fossil Record ◽  
Sea Urchins ◽  
Geographical Range ◽  
Speciation Rate ◽  
Developmental Mode ◽  
Ascidian Species ◽  
Speciation Rates

Ascidian species (Tunicata: Ascidiacea) usually have tailed, hatching tadpole larvae. In several lineages, species have evolved larvae that completely lack any tail tissues and are unable to disperse actively. Some tailless species hatch, but some do not hatch before going through metamorphosis. We show here that ascidian species with the highest speciation rates are those with the largest range sizes and tailed hatching larval development. We use methods for examining diversification in binary characters across a posterior distribution of trees, and show that mode of larval development predicts geographical range sizes. Conversely, we find that species with the least dispersive larval development (tailless, non-hatching) have the lowest speciation rates and smallest geographical ranges. Our speciation rate results are contrary to findings from sea urchins and snails examined in the fossil record, and further work is necessary to reconcile these disparate results.

scholarly journals Coordinated shifts to non-planktotrophic development in spatangoid echinoids during the Late Cretaceous

2009 ◽  
Vol 5 (5) ◽  
pp. 647-650 ◽  
Author(s):  
John A. Cunningham ◽  
Charlotte H. Jeffery Abt
Keyword(s):  
Larval Development ◽  
Late Cretaceous ◽  
Fossil Record ◽  
Evolutionary History ◽  
Sea Urchins ◽  
Geological History ◽  
Extrinsic Factors ◽  
Genus Level ◽  
History Of ◽  
Widespread Interest

Despite widespread interest in the interplay between evolutionary and developmental processes, we still know relatively little about the evolutionary history of larval development. Many clades exhibit multiple shifts from planktotrophic (feeding) to non-planktotrophic (non-feeding) larval development. An important question is whether these switches are scattered randomly through geological history or are concentrated in particular intervals of time. This issue is addressed using the Cretaceous spatangoid sea urchins, which are unusual in that larval strategy can be determined unambiguously from abundantly fossilized adult tests. Using a genus-level phylogeny, we identify five clades of non-planktotrophic taxa, each of which first appears in the fossil record in the Campanian or Maastrichtian (the final two Cretaceous stages). No examples of non-planktotrophy have been identified in any of the earlier stages of the Cretaceous. This strongly suggests that shifts to non-planktotrophic development are clustered in certain episodes of geological history, and this, in turn, implies that extrinsic factors operating at these times are responsible for driving shifts in developmental strategy.

scholarly journals What affects power to estimate speciation rate shifts?

2018 ◽  
Author(s):  
Ullasa Kodandaramaiah ◽  
Gopal Murali
Keyword(s):  
Evolutionary Biology ◽  
Ecological Factors ◽  
Tree Age ◽  
Character State ◽  
Speciation Rate ◽  
Relative Age ◽  
Rate Shift ◽  
Rate Asymmetry ◽  
Bias Ratio ◽  
Speciation Rates

The development of methods to estimate rates of speciation and extinction from time- calibrated phylogenies has revolutionized evolutionary biology by allowing researchers to correlate diversification rate shifts with causal ecological factors. A growing number of researchers are interested in testing whether the evolution of a trait or a trait variant has influenced speciation rates, and three modelling methods – BiSSE, MEDUSA and BAMM – have been widely used in such studies. We simulated phylogenies with a single speciation rate shift each, and evaluated the power of the three methods to detect these shifts. We varied the degree of increase in speciation rate (rate asymmetry), the number of tips, the tip-ratio bias (ratio of number of tips with each character state) and the relative age in relation to overall tree age when the rate shift occurred. All methods had good power to detect rate shifts when the rate asymmetry was strong and the sizes of the two lineages with the distinct speciation rates were large. Even when lineage size was small, power was good when rate asymmetry was high. In our simulated scenarios, small lineage sizes appear to affect BAMM most strongly. Tip-ratio influenced the accuracy of speciation rate estimation but did not have a strong effect on power to detect rate shifts. Based on our results, we provide some suggestions to users of these methods.

scholarly journals How predictable is extinction? Forecasting species survival at million-year timescales

2019 ◽  
Vol 374 (1788) ◽  
pp. 20190392 ◽  
Author(s):  
Peter Smits ◽  
Seth Finnegan
Keyword(s):  
Fossil Record ◽  
Human Impacts ◽  
Rank Order ◽  
Extinction Risk ◽  
Geographical Range ◽  
The Past ◽  
The Future ◽  
Out Of Sample ◽  
Extinction Events ◽  
Over Time

A tenet of conservation palaeobiology is that knowledge of past extinction patterns can help us to better predict future extinctions. Although the future is unobservable, we can test the strength of this proposition by asking how well models conditioned on past observations would have predicted subsequent extinction events at different points in the geological past. To answer this question, we analyse the well-sampled fossil record of Cenozoic planktonic microfossil taxa (Foramanifera, Radiolaria, diatoms and calcareous nanoplankton). We examine how extinction probability varies over time as a function of species age, time of observation, current geographical range, change in geographical range, climate state and change in climate state. Our models have a 70–80% probability of correctly forecasting the rank order of extinction risk for a random out-of-sample species pair, implying that determinants of extinction risk have varied only modestly through time. We find that models which include either historical covariates or account for variation in covariate effects over time yield equivalent forecasts, but a model including both is overfit and yields biased forecasts. An important caveat is that human impacts may substantially disrupt range-risk dynamics so that the future will be less predictable than it has been in the past. This article is part of a discussion meeting issue ‘The past is a foreign country: how much can the fossil record actually inform conservation?’

Quantifying morphological change during an evolutionary radiation of Devonian trilobites

Paleobiology ◽  
2012 ◽  
Vol 38 (2) ◽  
pp. 292-307 ◽  
Author(s):  
Francine R. Abe ◽  
Bruce S. Lieberman
Keyword(s):  
Morphological Change ◽  
Fossil Record ◽  
Character State ◽  
Geometric Morphometric ◽  
Biogeographic Patterns ◽  
Ancestral Character State ◽  
Speciation Rates ◽  
Adaptive Radiations ◽  
Geometric Morphometric Analysis ◽  
Heterogeneous Region

The fossil record provides an important source of data on adaptive radiations, and indeed some of the earliest theoretical insights on the nature of these radiations were made by paleontologists. Here we focus on the diverse DevonianMetacryphaeusgroup calmoniid trilobites, known from the Malvinokaffric Realm, which have been considered a classic example of an adaptive radiation preserved in the fossil record. We use a geometric morphometric analysis in conjunction with phylogenetic and biogeographic patterns and data on speciation rates. Using ancestral character state reconstruction during speciation events, we quantify patterns of morphological change in order to assess the role ecological and geographical factors may have played in mediating this radiation. We found no significant differences between the amount of morphological change that occurred during speciation events when ancestors and descendants were in the same area as opposed to when they occupied different areas. Further, the magnitude of morphological divergence did not change through time or with cladogenetic rank. These patterns, in conjunction with the fact that the radiation occurs in a geographically heterogeneous region subjected to repeated episodes of sea-level rise and fall, suggest that at the macroevolutionary scale this radiation may have been motivated more by phenomena that facilitated geographic isolation than by competition.

scholarly journals Bacterial community dynamics during embryonic and larval development of three confamilial echinoids

2018 ◽  
Author(s):  
Tyler J. Carrier ◽  
Adam M. Reitzel
Keyword(s):  
Bacterial Community ◽  
Larval Development ◽  
Bacterial Communities ◽  
Community Dynamics ◽  
Marine Invertebrates ◽  
Sea Urchins ◽  
Larval Feeding ◽  
Bacterial Community Dynamics ◽  
Future Work ◽  
Embryonic And Larval Development

ABSTRACTDevelopment of some animals is influenced by and, in some cases, dependent on the associated microbiota. The timing of when associated bacterial communities are established during the development of marine invertebrates and their subsequent dynamics across stages are known for only a few species. Here, we compare the bacterial communities of three confamilial echinoids from egg to juvenile using sequence-based approaches. Bacterial communities are established on unfertilized eggs and change gradually during embryonic and larval development. Despite the differences amongst these pre-metamorphic stages, approximately thirty-percent of OTUs identified in association with unfertilized egg were present in the juveniles. During embryonic development, host-associated communities diverged from the environmental microbiota but later converged following the onset of larval feeding. Taken together, the data presented here support the hypothesis that bacterial communities are established prior to fertilization and community composition shifts gradually thereafter, all while remaining distinct from the environment. Future work will need to determine the relative influence of the host and bacteria-bacteria interactions in shaping the associated bacterial community to determine the potential functional importance of bacteria during the development of larval sea urchins and benthic marine invertebrates more broadly.

scholarly journals Embryonic and larval development is conditioned by water temperature and maternal origin of eggs in the sea urchin Arbacia dufresnii (Echinodermata: Echinoidea)

2021 ◽  
Vol 69 (Suppl.1) ◽  
pp. 452-463
Author(s):  
Jimena Pía-Fernández ◽  
Florencia Belén-Chaar ◽  
Lucía Epherra ◽  
Jorge-Marcelo González-Aravena ◽  
Tamara Rubilar
Keyword(s):  
Larval Development ◽  
Embryo Development ◽  
Linear Models ◽  
Sea Urchins ◽  
Seawater Temperature ◽  
Larval Growth ◽  
Temperature Treatment ◽  
High Temperature Treatment ◽  
Larval Size ◽  
Embryonic And Larval Development

Introduction: Embryonic and larval development in sea urchins is highly dependent on maternal nutritional status and on the environmental conditions of the seawater. Objective: To compare the development of Arbacia dufresnii in two different water temperatures and in progeny with varying maternal origins. Methods: We induced A. dufresnii females and males from Nuevo Gulf to spawn, collected the eggs of each female individually (progeny), separated them into two seawater temperatures (12 and 17 °C), and fertilized them. We recorded the percentage of fertilized eggs and embryos per developmental stage according to time, temperature and progeny. We measured larval growth by total length (TL) and midline body length (M) according to time post fecundation (DPF), temperature, and progeny. Results: Temperature did not affect fertilization, but embryo development was faster and more synchronized in the high temperature treatment. The generalized linear models indicate that embryo development depends on a quadruple interaction between the embryonic stage, time (h), seawater temperature and progeny. Larval growth was faster, producing larger larvae at the highest temperature. Larval growth depends on a triple interaction between time (DPF), seawater temperature and progeny. Conclusions: We found a temperature and progeny impact during embryonic and larval development and, in both cases, these factors generate a synergistic effect on developmental timing and larval size. This probably provides a survival advantage as a more rapid speed of development implies a decrease in the time spent in the water column, where the sea urchins are vulnerable to biotic and abiotic stressors.

Towards a scientific-based farming of sea urchins: First steps in the cultivation of Diadema setosum, Diadema savignyi and Mesocentrotus nudus

2020 ◽  
Author(s):  
Salim Dautov ◽  
Tatiana Dautova ◽  
Svetlana Kashenko
Keyword(s):  
South China Sea ◽  
Larval Development ◽  
South China ◽  
Sea Urchins ◽  
Japan Sea ◽  
Tropical Zone ◽  
Cultivated Species ◽  
Mesocentrotus Nudus ◽  
Pluteus Stage ◽  
Diadema Setosum

FISHING OR BREEDING. This question arose relatively recently, but in the last decade, mankind will have to lean more towards the second. Sea reserves of useful species are exhausted. One possible solution to this problem is marine farming. We proposed to investigate the larval development of three sea urchin species: Diadema setosum (Leske, 1778), D. savignyi (Audouin, 1829) (South China Sea), and Mesocentrotus nudus (A. Agassiz, 1864) (Japan Sea). The larvae of Diadema setosum and D. savignyi were very similar, and some differences could only be observed at the late pluteus stage. These sea urchins were developed through the modified pluteus, which only had two pairs of larval arms. The arms were very long - in D. setosum above 2 mm, and in D. savignyi about 5.5 mm. Larval development took about 45 days in D. setosum and 47–50 days in D. savignyi. In contrast, Mesocentrotus nudus (A. Agassiz, 1864) was developed through the pluteus larvae, which had some differences from the pluteus of the genus Strongylocentrotus. Their dimensions did not reach one millimetre. The larval development of Mesocentrotus nudus lasted about 30 days. Analysis of material and time costs has led to the conclusion that Mesocentrotus nudus is the most convenient for obtaining seed material. However, this species cannot be used for the tropical zone. The results of D. savignyi and D. setosum can be used to increase the number of cultivated species.

scholarly journals Positive association between population genetic differentiation and speciation rates in New World birds

2017 ◽  
Vol 114 (24) ◽  
pp. 6328-6333 ◽  
Author(s):  
Michael G. Harvey ◽  
Glenn F. Seeholzer ◽  
Brian Tilston Smith ◽  
Daniel L. Rabosky ◽  
Andrés M. Cuervo ◽  
...  
Keyword(s):  
Population Differentiation ◽  
New World ◽  
Bird Species ◽  
Positive Association ◽  
Tropical Species ◽  
Implicit Assumption ◽  
Speciation Rate ◽  
Population Genetic Differentiation ◽  
Evolutionary Diversification ◽  
Speciation Rates

An implicit assumption of speciation biology is that population differentiation is an important stage of evolutionary diversification, but its significance as a rate-limiting control on phylogenetic speciation dynamics remains largely untested. If population differentiation within a species is related to its speciation rate over evolutionary time, the causes of differentiation could also be driving dynamics of organismal diversity across time and space. Alternatively, geographic variants might be short-lived entities with rates of formation that are unlinked to speciation rates, in which case the causes of differentiation would have only ephemeral impacts. By pairing population genetics datasets from 173 New World bird species (>17,000 individuals) with phylogenetic estimates of speciation rate, we show that the population differentiation rates within species are positively correlated with their speciation rates over long timescales. Although population differentiation rate explains relatively little of the variation in speciation rate among lineages, the positive relationship between differentiation rate and speciation rate is robust to species-delimitation schemes and to alternative measures of both rates. Population differentiation occurs at least three times faster than speciation, which suggests that most populations are ephemeral. Speciation and population differentiation rates are more tightly linked in tropical species than in temperate species, consistent with a history of more stable diversification dynamics through time in the Tropics. Overall, our results suggest that the processes responsible for population differentiation are tied to those that underlie broad-scale patterns of diversity.

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