Dynamics of core and occasional species in the marine plankton: tintinnid ciliates in the north‐west Mediterranean Sea

Abstract

Aim To assess short-term variability in the community composition and community structure of tintinnid ciliates, herbivores of the microzooplankton.Location North-west Mediterranean Sea.Methods We sampled on 18 dates over a 4-week period in 2004 at an openwater site. Species were classified as 'core species', found on every date, or 'occasional species', absent on one or more dates. Species abundance distributions of the entire community, and separately the core and occasional species, were compared with geometric, log-series and log-normal distributions. Core and occasional species were compared in terms of the shell or lorica oral diameter (LOD), analogous to gape size. ResultsWe found 11 core and 49 occasional species. Diversity metrics were stable compared with shifts in abundances. Core species accounted for the majority of individuals in all samples. On each date, 9-22 occasional species, representing 10-15% of the population, were found. Species richness of the occasionals was positively related to population size. The identities of the occasional species found were unrelated to the time between sampling. The species abundance distribution of the occasional population was best fit by a log-series distribution, while that of the core species was best fit by a log-normal distribution. The species abundance distribution of the entire community was best fit by a log-series distribution. Most of the occasional species had LODs distinct from that of a core species and occupied size classes left empty by the core population. However, the most abundant and frequent of the occasional species had a LOD similar to that of a core species.Main conclusions Among tintinnids, which are planktonic protists, occasional species have a species abundance distribution pattern distinct from that of core species. Occasional species appeared to be composed of two groups, one of relatively abundant species and similar to core species, and a second group of ephemeral species with morphologies distinct from core species. The existence of two categories of occasional or rare species may be common: (1) those similar to, and thus perhaps able to replace, dominant species in the absence of a change in the environment; and (2) those distinct from dominant species and requiring different conditions to prosper.

Reducing bias in bacterial community analysis of lower respiratory infections

“…This would indicate that skewed observations of local community composition are reached without prior PMA treatment. The effects of PMA treatment at the metacommunity level At the metacommunity level, it has been established that a dichotomy exists within metacommunity species abundance distributions (SADs), consisting of 'regionally' common and locally abundant core species and infrequent rare satellite species groups (for example, Magurran and Henderson, 2003;Ulrich and Zalewski, 2006;Dolan et al, 2009;Unterseher et al, 2011). Recently, we established that the core-satellite group approach can be applied to CF bacterial communities and that partitioning the two groups from a metacommunity revealed important aspects of SADs, which would otherwise be neglected without such a distinction (van der Gast et al, 2011).…”

Patterns and processes in microbial biogeography: do molecules and morphologies give the same answers?

“…Even if water mixing is expected to transport species across the shelf, environmental selection could prevent establishment (growth) when conditions are non-optimal, and thus limit the successful dispersal (colonization) in the new environment. An additional or alternative process operating on the shelf may be drift (for example, random dispersal), especially in determining the distribution of ecologically similar species within inshore, offshore and deep waters (Dolan et al, 2007(Dolan et al, , 2009). …”

“…Indeed, assemblages of tintinnid morphospecies differ markedly in the bathymetric, latitudinal and vertical profiles (for example, Alder, 1999;Modigh et al, 2003;Santoferrara and Alder, 2012), as well as in the seasonal cycle of temperate coasts (for example, Bojanić et al, 2012). Structuring of morphospecies assemblages has been explained by environmental selection in a coastal site (Sitran et al, 2009) or random dispersal in open waters (Dolan et al, 2007(Dolan et al, , 2009(Dolan et al, , 2013b, but the processes that affect assembly in the transitions between environments are unknown. Likewise, it is not known whether patterns and processes based on morphologies and molecules agree, as few distribution studies have used DNA sequences to target tintinnids and aloricate sister lineages (Doherty et al, 2010;Tamura et al, 2011;Bachy et al, 2014;Grattepanche et al, 2015).…”

Short-scale temporal variability of physical, biological and biogeochemical processes in the NW Mediterranean Sea: an introduction

“…Recalling the patterns found among diatoms and dinoflagellates (Lasternas et al, 2008), the number of species found on each sampling date varied within a narrow range while the identity of the taxa changed (Dolan et al, 2009). However, the identity of the most common "core" species, representing a small part of the species lists but accounting for the overwhelming majority of individuals, was invariant, a pattern also described for the large (>500 µm) copepods (Raybaud et al, 2008b).…”