The temporal dimension of marine speciation

Abstract

Speciation is a process that occurs over time and, as such, can only be fully understood in an explicitly temporal context. Here we discuss three major consequences of speciation's extended duration. First, the dynamism of environmental change indicates that nascent species may experience repeated changes in population size, genetic diversity, and geographic distribution during their evolution. The present characteristics of species therefore represents a static snapshot of a single time point in a species' highly dynamic history, and impedes inferences about the strength of selection or the geography of speciation. Second, the process of speciation is open ended-ecological divergence may evolve in the space of a few generations while the fixation of genetic differences and traits that limit outcrossing may require thousands to millions of years to occur. As a result, speciation is only fully recognized long after it occurs, and short-lived species are difficult to discern. Third, the extinction of species or of clades provides a simple, under-appreciated, mechanism for the genetic, biogeographic, and behavioral 'gaps' between extant species. Extinction also leads to the systematic underestimation of the frequency of speciation and the overestimation of the duration of species formation. Hence, it is no surprise that a full understanding of speciation has been difficult to achieve. The modern synthesis-which united genetics, development, ecology, biogeography, and paleontologygreatly advanced the study of evolution. Here we argue that a similarly synthetic approach must be taken to further our understanding of the origin of species.

Owenia caissara sp. n. (Annelida, Oweniidae) from Southern Brazil: addressing an identity crisis

“…By describing a new species from southern Brazil, previously referred to as O. fusiformis, we reinforce the growing understanding of the large worldwide diversity of Owenia, supporting that the existing environmental barriers effectively limit larval dispersal (Norris and Hull 2012). Taxonomically robust morphological characters allowed for the unambiguous recognition of a new taxon, contributing to mitigate a true identity crisis still persistent in the regional literature.…”

Parallel changes in genital morphology delineate cryptic diversification of planktonic nudibranchs

“…terrestrial) speciation models in the open ocean [3][4][5][6], and is the first to reveal a specific, biologically driven isolating barrier in a planktonic group. It also provides new insights into the benthic evolutionary origins of the neustonic Glaucinae.…”

“…How is pelagic biodiversity generated? Proposed speciation mechanisms in pelagic sibling species complexes are essentially variations on two classic themes: the geographical isolation of populations (allopatry) or nongeographical genetic isolation mechanisms (non-allopatry) [3,4]. The greatest obstacles to testing these hypotheses are sampling limitations for representative collections of cosmopolitan groups, and a related paucity of morphological data for marine taxa, leading to difficulty identifying species [5,6].…”

Tracking niche variation over millennial timescales in sympatric killer whale lineages

“…Most evolutionary studies typically use either comparisons at a single point in time or over timescales representing one to a few generations [15][16][17] or infer ancestral states using phylogenetic-based methods [18]. This snapshot of evolution may only be partially informative, as throughout the speciation process, diverging populations may have experienced changes in ecological conditions, geographical distribution and population size that could have influenced the strength of selection and the rate of progress towards speciation [19][20][21][22]. However, real-time tracking of niche width in long-lived species over evolutionary and ecological timescales can be achieved by the incorporation of ancient DNA (aDNA) and stable isotope data from subfossil specimens [23].…”