Is the evolution of carnivory connected with genome size reduction?

Abstract

As repeatedly shown, the remarkable variation in the genome size of angiosperms can be shaped by extrinsic selective pressures, including nutrient availability. Carnivory has evolved independently in 10 angiosperm clades, but all carnivorous plants share a common affinity to nutrient-poor habitats. As such, carnivory and genome reduction could be responses to the same environmental pressure. Indeed, the smallest genomes among flowering plants are found in the carnivorous family Lentibulariaceae, where a unique mutation in cytochrome c oxidase (COX) is suspected to promote genome miniaturization. Despite these hypotheses, a phylogenetically informed test of genome size and nutrient availability across carnivorous clades has so far been missing. METHODS: Using linear mixed models, we compared genome sizes of 127 carnivorous plants from 7 diverse angiosperm clades with 1072 of their noncarnivorous relatives. We also tested whether genome size in Lentibulariaceae reflects the presence of the COX mutation. RESULTS: The genome sizes of carnivorous plants do not differ significantly from those of their noncarnivorous relatives. Based on available data, no significant association between the COX mutation and genome miniaturization could be confirmed, not even when considering polyploidy. CONCLUSIONS: Carnivory alone does not seem to significantly affect genome size decrease. Plausibly, it might actually counterbalance the effect of nutrient limitation on genome size evolution. The role of the COX mutation in genome miniaturization needs to be evaluated by analysis of a broader data set because current knowledge of its presence across Lentibulariaceae covers less than 10% of the species diversity in this family.

Genome downsizing after polyploidy: mechanisms, rates and selection pressures

“…Genlisea and Utricularia ), which typically have a streamlined genome, perhaps due to evolutionary or ecological selection on GS in low‐nutrient environments (Veleba et al. , 2020).…”

The global distribution of angiosperm genome size is shaped by climate

“…Finally, nutrient limitation might play a role in constraining the genome size of tropical plants, as many tropical soils are low in nutrients (especially P; Vitousek et al ., 2010), and yet building and maintaining cells in plants with large genomes is expensive in terms of N and P. This may result in species with large genomes being less competitive in the nutrient‐poor tropical soils, resulting in their exclusion from these environments (Leitch & Leitch, 2008; Šmarda et al ., 2013; Guignard et al ., 2016; Veleba et al ., 2020; Faizullah et al ., 2021).…”

Determination of Chromosome Numbers and Genome Sizes in Six Species of <i>Byblis</i> (Byblidaceae)

“…In comparison to chromosome study, only a few researchers have experimentally determined the genome sizes (Table 2): 1C of B. gigantea was 495 Mbp (Veleba et al 2020), while 1C of B. liniflora was 870 Mbp (Hanson et al 2001) and 884 Mbp (Veleba et al 2020). Combining previous chromosome information with monomodal karyotypes (Hoshi et al 2007, Fukushima et al 2008, these data give us the estimation that the diploid B. gigantea and the tetraploid B. liniflora possess haploid C-value (1Cx) DNA contents of 495 Mbp and ca.…”

“…Nuclear DNA content (C-value), showing genome size with a specific karyological feature, is useful for addressing systematic and evolutionary questions Leitch 1995, 2011). Compared with the proactive chromosome research of Byblis, there is still a lack of information on the C-values in this genus, except for B. gigantea (Veleba et al 2020) and B. liniflora (Hanson 2001, Veleba et al 2020).…”