Speciation in Hawaiian Angiosperm Lineages: Cause, Consequence, and Mode

Abstract

Abstract. The biota of Hawaiian Islands is derived entirely from long distance dispersal, often followed by in situ speciation. Species descended from each colonist constitute monophyletic lineages that have diverged to varying degrees under similar spatial and temporal constraints. We partitioned the Hawaiian angiosperm flora into lineages and assessed morphological, ecological, and biogeographic characteristics to examine their relationships to variation in species number (S). Lineages with external bird dispersal (through adhesion) were significantly more species-rich than those with abiotic dispersal, but only weakly more species-rich than lineages with internal bird dispersal (involving fleshy fruits). Pollination mode and growth form (woody vs. herbaceous) had no significant effect on S, in contrast to studies of angiosperm families. S relates positively to the geographic and ecological range size of whole lineages, but negatively to local abundance and mean range sizes of constituent species. Species-rich lineages represent a large proportion of major adaptive shifts, although this appears to be an artifact of having more species. Examination of 52 sister species pairs in numerous lineages provides evidence for allopatric (including peripheral isolates) and parapatric (ecological) modes, with 15 cases of each. Although postspeciational dispersal may obscure these modes in many of the remaining cases, instances of sympatric and hybrid speciation are also discussed. Because speciation is both a consequence and a cause of ecological and biogeographic traits, speciation mode may be integral to relationships between traits. We discuss the role of speciation in shaping the regional species pool.

Ancient Dispersals, Propagule Pressure, and Species Selection in Flowering Plants

“…Although it follows that species with the largest ranges would have the most plants and thus produce the most propagules, my argument is strengthened by the observation that species with larger geographical distributions tend to have greater local abundances, i.e., larger numbers and sizes of populations (Brown 1984;Harte et al 2001;Brown 1995;Gaston 2003). This relationship is well documented in the Hawaiian flora (Sakai et al 2002;Price and Wagner 2004). Accordingly, propagule production is not only correlated with expanding range size; propagule production increases per unit area.…”

“…Sister species in the Hawaiian archipelago (Price and Wagner 2004) and within the Juan Fernandez Islands (Stuessey et al 1998) strongly tend to occur in similar habitats.…”

Adaptive radiation of photosynthetic physiology in the Hawaiian lobeliads: dynamic photosynthetic responses

“…While there have been tremendous advances in our knowledge of the origin and phylogeny of Hawaiian plant and animal radiations (e.g., see Baldwin et al 1991;Givnish et al 1995;Piano et al 1997;Lindqvist et al 2003;Gillespie 2004;Price and Wagner 2004;Rundell et al 2004;Sakai et al 2006), for many of these radiations we lack the functional data necessary to understand the ecological signiWcance of phenotypic divergences seen within them. A body of work has developed on functional trait variation in Hawaiian plant radiations, notably on Euphorbia and Scaevola (Robichaux andPearcy 1980, 1984;Pearcy et al 1982), the silversword alliance (Robichaux 1984;Robichaux and CanWeld 1985;Robichaux et al 1990), and Schiedea (Sakai et al 2006).…”

Trait convergence and diversification arising from a complex evolutionary history in Hawaiian species of Scaevola

“…Species radiations and diversifications often show adaptation to environmental factors, with trait changes associated with selective pressures (including both abiotic and biotic factors) (Price and Wagner 2004;Rundell and Price 2009; Kraft et al 2015). Previous studies of Scaevola ecological distributions have tended to focus on elevation (Patterson 1990;Howarth and Baum 2005).…”