Phylogenomics resolves the relationships within Antennaria (Asteraceae, Gnaphalieae) and yields new insights into its morphological character evolution and biogeography

Antennaria are dioecious perennial herbs distributed mainly in the
Holarctic Region with their major center of diversity in the Rocky
Mountains of Western North America. The genus comprises 33 known sexual
diploid/tetraploid species and at least five polyploid agamic complexes
which mostly reproduce by forming asexual seeds. We performed a
phylogenetic reconstruction of the 31 sexually-reproducing Antennaria
species using a novel target enrichment method that employs custom capture
probes and is designed to work across Asteraceae. Both concatenated and
coalescent-based analyses of DNA sequence data from hundreds of nuclear
loci recovered Antennaria as a monophyletic group except for the
long-disputed species, Antennaria linearifolia, which was recovered
outside of the genus. Antennaria was further resolved into three distinct,
major lineages. Analysis of ancestral state reconstruction of 12
taxonomically important morphological characters elucidated patterns of
character evolution throughout the genus. Estimations of ancestral
geographic ranges and molecular dating analyses demonstrated the Rocky
Mountain region, including the Vancouverian Province, as the center of
origin for the genus Antennaria, around 5.8 MYA. Subsequent dispersals of
Antennaria into the Arctic and Appalachian provinces, Canadian provinces,
and Eurasia took place roughly 3.2 MYA, 2.4 MYA and 1.6 MYA, respectively.
Biogeographical Stochastic Mapping indicated that 51.4% of biogeographical
events were based on within-area speciation. The remaining 48.6% of the
events were divided into two types of dispersals: i) range expansion
dispersals (anagenic, 37%) and ii) founder/jump dispersals (cladogenic,
11.6%). Our results provide a framework for future evolutionary studies of
Antennaria, including speciation, origin(s) of polyploidy, and agamospermy
in the genus.

蝶须属（Antennaria）为雌雄异株的多年生草本植物，主要分布于全北界（Holarctic Region），其多样性中心集中在北美西部的落基山脉。该属包含33种已知的有性繁殖二倍体/四倍体物种，以及至少5个多倍体无融合生殖复合体，后者大多通过形成无性种子繁殖。我们采用一种新型靶标富集方法（该方法使用定制捕获探针，且适用于菊科（Asteraceae）植物），对31种有性繁殖的蝶须属物种进行了系统发育重建。对数百个核基因座的DNA序列数据进行的串联分析和基于溯祖（coalescent）的分析均表明，蝶须属是一个单系群，但长期存在争议的物种——线叶蝶须（Antennaria linearifolia）除外，该物种被发现位于蝶须属之外。蝶须属进一步被划分为3个明显的主要谱系。对12个分类学重要形态性状的祖先状态重建分析，阐明了该属内性状演化的模式。祖先地理分布范围估计和分子定年分析表明，包括温哥华省在内的落基山脉地区是蝶须属的起源中心，时间约在580万年前（MYA）。随后，蝶须属向北极和阿巴拉契亚地区、加拿大各省以及欧亚大陆的扩散分别发生在约320万年前、240万年前和160万年前。生物地理随机映射（Biogeographical Stochastic Mapping）分析表明，51.4%的生物地理事件基于区域内物种形成。其余48.6%的事件分为两类扩散：i) 范围扩张扩散（渐进式，37%）和 ii) 奠基者/跳跃扩散（分支式，11.6%）。我们的研究结果为蝶须属未来的演化研究提供了框架，包括该属的物种形成、多倍体起源以及无融合生殖等方面。