How discordant morphological and molecular evolution among microorganisms can revise our notions of biodiversity on Earth

Abstract

Microscopy has revealed a tremendous diversity of bacterial and eukaryotic forms. More recent molecular analyses show discordance in estimates of biodiversity based on morphological analyses. Moreover, phylogenetic analyses of the diversity of microbial forms have revealed evidence of convergence at scales as large as interdomain – i.e. convergent forms shared between bacteria and eukaryotes. Here, we highlight examples of such discordance, focusing on exemplary lineages such as testate amoebae, ciliates and cyanobacteria, which have long histories of morphological study. We discuss examples in two categories: 1) morphologically identical (or highly similar) individuals that are genetically distinct and 2) morphologically distinct individuals that are genetically distinct. We argue that hypotheses about discordance can be tested using the concept of neutral morphologies, or more broadly neutral phenotypes, as a null hypothesis.

On the evolution of bacterial multicellularity

“…Archaeal biofilms, for example, contain many of the same features as bacteria biofilms: cell differentiation, filamentation, and even the same general matrix components [56–58]. The same can be said of deceptively similar morphological structures like fruiting bodies in myxobacteria, which resemble the fruiting bodies formed by many amoeba species [59]. These structures are physically similar and are even thought to serve the same purpose (spore dispersal), yet share no underlying homology other than cell motility.…”

Uncovering Cryptic Diversity in Two Amoebozoan Species Using Complete Mitochondrial Genome Sequences

“…Statistically powerful, multigene phylogenetic studies are essential, because they can change our perception of evolutionary histories that are clouded by morphological convergence (Lahr et al. ).…”

Insights into transgenerational epigenetics from studies of ciliates

“…Similarly, differential loss of duplicated macronuclear destined sequences, which can be corrected through gene unscrambling and alternative processing, may inhibit production of viable offspring between members of previously isolated populations (Gao et al, 2015). This rapid speciation as the result of epigenetic processes may contribute to the complex patterns of morphological and molecular evolution such as cryptic species, which are common in ciliates (Foissner et al, 2008; Hall and Katz, 2011; Lahr et al, 2014; Przybos and Tarcz, 2016; Sonneborn, 1975). …”