Data from: Evolution of dispersal, habit, and pollination in Africa pushed Apocynaceae diversification after the Eocene-Oligocene climate transition

Apocynaceae (the dogbane and milkweed family) is one of the ten largest
flowering plant families, with approximately 5,350 species and diverse
morphology and ecology, ranging from large trees and lianas that are
emblematic of tropical rainforests, to herbs in temperate grasslands, to
succulents in dry, open landscapes, and to vines in a wide variety of
habitats. Despite a specialized and conservative basic floral
architecture, Apocynaceae are hyperdiverse in flower size, corolla shape,
and especially derived floral morphological features. These are mainly
associated with the development of corolline and/or staminal coronas and a
spectrum of integration of floral structures culminating with the
formation of a gynostegium and pollinaria—specialized pollen dispersal
units. To date, no detailed analysis has been conducted to estimate the
origin and diversification of this lineage in space and time. Here, we use
the most comprehensive time-calibrated phylogeny of Apocynaceae, which
includes approximately 20% of the species covering all major lineages, and
information on species number and distributions obtained from the most
up-to-date monograph of the family to investigate the biogeographical
history of the lineage and its diversification dynamics. South America,
Africa, and Southeast Asia (potentially including Oceania), were recovered
as the most likely ancestral area of extant Apocynaceae diversity; this
tropical climatic belt in the equatorial region retained the oldest extant
lineages and these three tropical regions likely represent museums of the
family. Africa was confirmed as the cradle of pollinia-bearing lineages
and the main source of Apocynaceae intercontinental dispersals. We
detected 12 shifts toward accelerated species diversification, of which 11
were in the APSA clade (apocynoids, Periplocoideae, Secamonoideae, and
Asclepiadoideae), eight of these in the pollinia-bearing lineages and six
within Asclepiadoideae. Wind-dispersed comose seeds, climbing growth form,
and pollinia appeared sequentially within the APSA clade and probably work
synergistically in the occupation of drier and cooler habitats. Overall,
we hypothesize that temporal patterns in diversification of Apocynaceae
was mainly shaped by a sequence of morphological innovations that
conferred higher capacity to disperse and establish in seasonal, unstable,
and open habitats, which have expanded since the Eocene-Oligocene climate
transition.