Data from: Out of the Orient: Post-Tethyan transoceanic and trans-Arabian routes fostered the spread of Baorini skippers in the Afrotropics

The origin of taxa presenting a disjunct distribution between Africa and
Asia has puzzled biogeographers for more than a century. This
biogeographic pattern has been hypothesized to be the result of
transoceanic long‐distance dispersal, Oligocene dispersal through forested
corridors, Miocene dispersal through the Arabian Peninsula or passive
dispersal on the rifting Indian plate. However, it has often been
difficult to pinpoint the mechanisms at play. We investigate biotic
exchange between the Afrotropics and the Oriental region during the
Cenozoic, a period in which geological changes altered landmass
connectivity. We use Baorini skippers (Lepidoptera, Hesperiidae) as a
model, a widespread clade of butterflies in the Old World tropics with a
disjunct distribution between the Afrotropics and the Oriental region. We
use anchored phylogenomics to infer a robust evolutionary tree for Baorini
skippers and estimate divergence times and ancestral ranges to test
biogeographic hypotheses. Our phylogenomic tree recovers strongly
supported relationships for Baorini skippers and clarifies the systematics
of the tribe. Dating analyses suggest that these butterflies originated in
the Oriental region, Greater Sunda Islands, and the Philippines in the
early Miocene c. 23 Ma. Baorini skippers dispersed from the Oriental
region towards Africa at least five times in the past 20 Ma. These
butterflies colonized the Afrotropics primarily through trans‐Arabian
geodispersal after the closure of the Tethyan seaway in the mid‐Miocene.
Range expansion from the Oriental region towards the African continent
probably occurred via the Gomphotherium land bridge through the Arabian
Peninsula. Alternative scenarios invoking long‐distance dispersal and
vicariance are not supported. The Miocene climate change and biome shift
from forested areas to grasslands possibly facilitated geodispersal in
this clade of butterflies.

非洲与亚洲间呈现间断分布的类群起源问题，已困扰生物地理学界逾一个世纪。该生物地理格局被推测为以下四种成因之一：跨洋长距离扩散、渐新世（Oligocene）通过森林廊道扩散、中新世（Miocene）通过阿拉伯半岛扩散，或是在张裂的印度板块上发生被动扩散。然而，过往研究往往难以精准确定其背后的作用机制。

我们聚焦新生代（Cenozoic）时期非洲热带区（Afrotropics）与东洋区（Oriental region）之间的生物交换事件——这一地质时期内，地质变化重塑了各陆块的连通性。我们以宝弄蝶族（Baorini skippers）（鳞翅目（Lepidoptera），弄蝶科（Hesperiidae））作为研究模型，该类群是旧世界热带地区广泛分布的蝴蝶支系，在非洲热带区与东洋区间呈现间断分布格局。我们利用锚定系统发育组学（anchored phylogenomics）技术重建宝弄蝶族的稳健进化树，并估算分化时间与祖先分布区，以此验证相关生物地理假说。

我们的系统发育组学树解析了宝弄蝶族高支持度的系统发育关系，并厘清了该族的分类系统。分化时间分析显示，该类群起源于中新世早期（约2300万年前）的东洋区、大巽他群岛与菲律宾群岛。在过去2000万年间，宝弄蝶族至少五次从东洋区向非洲大陆扩散。这些蝴蝶主要通过中新世中期特提斯海道（Tethyan seaway）闭合后的跨阿拉伯陆桥扩散，成功定居非洲热带区。从东洋区向非洲大陆的分布扩张，大概率是通过阿拉伯半岛的铲齿象陆桥（Gomphotherium land bridge）实现的。其他涉及长距离扩散与地理分异（vicariance）的假说均不被支持。中新世的气候变化与生物群区从森林向草原的转变，或许推动了该蝴蝶支系的陆地扩散。