When samples from a single taxonomic species are resolved as monophyletic, or coalescent, in a phylogenetic analysis of DNA sequences, this is often the basis for “cryptic” or otherwise overlooked plant species. Here, we examine ecological evolutionary reasons behind genetic patterns within plant species.. We suggest that coalescence or monophyly of conspecific genetic samples occurs more commonly in animal than plant clades, which implies that plant species are more likely to have some combination of larger effective population sizes from a population or genomic perspective, inhabit less dispersal-limited habitats or niches, or have evolutionary younger ages. For woody plant species, we suspect that dry environments are more dispersal limited than wetter environments. We give examples that suggest coalescence of conspecific plant samples likely occurs more often among genetic samples taken from isolated populations that are phylogenetically niche conserved to the succulent biome. This is in comparison to those taken from isolated plant populations that are niche conserved to tropical wet forests. However, these suggested patterns will be context dependent. Recency of evolution, large effective population sizes, or polyploid genomes could work against detecting coalescent patterns of conspecific genetic samples in plant taxa that are niche conserved to the succulent biome.