Hines Heather M
Department of Entomology, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA.
Syst Biol. 2008 Feb;57(1):58-75. doi: 10.1080/10635150801898912.
Bumble bees (Bombus) are a cold-adapted, largely alpine group that can elucidate patterns of Holarctic historical biogeography, particularly in comparison to the alpine plants with which they likely coevolved. A recently published molecular phylogeny of bumble bees provides uniquely comprehensive species sampling for exploring historical patterns of distribution and diversification. Using this phylogeny and detailed data on extant distributions, I reconstruct the historical distribution of bumble bees in a temporal framework, estimating divergence times using fossil data and molecular rates derived from the literature. The nearly comprehensive phylogeny allows assessment of the tempo of diversification within the bumble bees using lineage-through-time plots and diversification statistics, which have been performed with special consideration to confidence intervals. These analyses reveal movements of Bombus concordant with geographic and climatic events of the late Cenozoic. The initial diversification of extant bumble bee lineages was estimated at around 25 to 40 Ma, near the Eocene-Oligocene boundary 34 Ma, a period of dramatic global cooling. Dispersal-vicariance analysis (DIVA) predicted an Old World Bombus ancestor, with early diversification events largely restricted to the eastern Old World. The numerous intercontinental dispersal events occurred mostly in the direction of Old World to New World and North America to South America. Early movements from the Palearctic into the Nearctic most likely took place after 20 Ma and may have coincided with a period of Miocene cooling that gave rise to taiga habitat across Beringia. Subsequent dispersal between these regions is estimated to have occurred among boreal and tundra-adapted species mostly in the last 5 million years. Radiations are estimated in both Nearctic and Neotropical regions at approximately 6 to 8 Ma and after 3.5 Ma, concordant with the opening of land corridors between the continents.
熊蜂（Bombus）是一个适应寒冷气候的群体，主要分布在高山地区，它们能够阐明全北区历史生物地理学的模式，特别是与可能与其共同进化的高山植物相比。最近发表的熊蜂分子系统发育研究提供了独特的全面物种样本，用于探索分布和多样化的历史模式。利用这个系统发育和现存分布的详细数据，我在一个时间框架内重建了熊蜂的历史分布，使用化石数据和文献中得出的分子速率估计分歧时间。几乎全面的系统发育使得能够使用线系随时间变化图和多样化统计来评估熊蜂内部的多样化速度，在进行这些统计时特别考虑了置信区间。这些分析揭示了熊蜂的迁移与晚新生代的地理和气候事件相一致。现存熊蜂谱系的初始多样化估计在大约2500万至4000万年前，接近始新世 - 渐新世边界（3400万年前），这是一个全球急剧降温的时期。扩散 - 隔离分析（DIVA）预测了一个旧世界熊蜂祖先，早期多样化事件主要局限于旧世界东部。众多的洲际扩散事件大多发生在从旧世界到新世界以及从北美洲到南美洲的方向。早期从古北界进入新北界的迁移最有可能发生在2000万年后，并且可能与中新世降温期相吻合，这一时期在白令陆桥形成了泰加林栖息地。据估计，这些地区之间随后的扩散主要发生在适应北方和苔原的物种之间，大多是在过去500万年里。在新北界和新热带界的辐射估计分别在大约600万至800万年前以及350万年后，与各大洲之间陆桥的开放相一致。
