Untitled

Abstract

Haploid genome size (C-value) is correlated positively with cell size, and negatively with cell division rate, in a variety of taxa. Because these associations are causative, genome size has the potential to impact (and in turn, be influenced by) organism-level characters affected by variation in either of these cell-level parameters. One such organismal feature is development. Developmental rate, in particular, has been associated with genome size in numerous plant, vertebrate, and invertebrate groups. However, rate is only one side of the developmental coin; the other important component is complexity. When developmental complexity is held essentially constant, as among many plants, developmental rate is the visibly relevant parameter. In this case, genome size can impose thresholds on developmental lifestyle (and vice versa), as among annual versus perennial plants. When developmental rate is constrained (as during time-limited amphibian metamorphosis), complexity becomes the notable variable. An appreciation for this rate-complexity interaction has so far been lacking, but is essential for an understanding of the relationships between genome size and development. Moreover, such an expanded view may help to explain patterns of variation in taxa as diverse as insects and fish. In each case, a hierarchical approach is necessary which recognizes the complex interaction of evolutionary processes operating at several levels of biological organization.

Limb regeneration in a direct‐developing terrestrial salamander, Bolitoglossa ramosi (Caudata: Plethodontidae)

“…The genome size found for B. ramosi was 25 Gb, which is within those reported for the Bolitoglossine clade (21−76 Gb) (Gregory, 2002). If we compare the genome size of B. ramosi with the genome size of plethodontids where limb regeneration has been superficially described (Scadding, 1981) (Table 1), such as Plethodon cinereus (20−26 Gb), Desmognathus ochrophaeus (14−18 Gb), and Eurycea bislineata (20−25 Gb) (AmphibiaWeb, 2017), it is noticed that their genome sizes are very similar to that of B. ramosi .…”

“…The C ‐value has been described as an important aspect to consider during limb regeneration and has been implicated in other biological processes such as development, metabolism, cellular differentiation, the cell cycle, and growth (Sessions, 2008; Sessions & Larson, 1987). Additionally, some authors have found a significant positive correlation between genome size and cell size and a negative correlation with cell division rate (Gregory, 2002). To explore this phenomenon, we analyzed the genome size of B. ramosi .…”

Genome size in arthropods; different roles of phylogeny, habitat and life history in insects and crustaceans

“…The overall variability in genome size is less in insects than in crustaceans. As shown in previous studies (Gregory, 2002), most of this variation is found within the hemimetabolous insects. By comparison, the holometabolous insects have small genomes.…”

“…Gregory (2002) suggested a threshold of approximately 2 pg haploid DNA per cell above which holometabolic metamorphosis becomes constrained by larger genomes. No mechanistic explanation is given, and the argument is challenged by some clear departures from this rule, notably within the Coleoptera (cf.…”

“…The fact that different species or taxa display different patterns of genome–body size relation suggests the result of several processes, ranging from micro‐evolutionary adaptation to current environments, to the maintenance of phylogenetic ancient patterns (which may or may not reflect adaptive traits). Differences in genome size have also been linked with developmental complexity (Gregory, 2002), such as hemimetabolous vs. holometabolous development in insects (Gregory, 2005). …”