Mosaic evolution underlies feliform morphological disparity

Constraint is a fundamental concept in evolutionary theory. Morphology and ecology both are limited by functional, historical, and developmental factors to a subset of the theoretical range species could occupy. Cat-like carnivorans (Feliformia) offer a unique opportunity to investigate phenotypic constraint, as several feliform clades are purported to be limited to generalized ecomorphological roles, while others possessing extremely specialized durophagous (bone-crushing) and sabertooth morphology. We investigated the evolutionary history of feliforms by considering their phylogeny, morphological disparity and rates of evolution. We recover results that show a mosaic pattern exists in the degree of morphological disparity per anatomical region per clade and ecology. Non-hypercarnivores, such as viverrids (civets and genets), Malagasy euplerids and lophocyonids (extinct hypocarnivores) have the greatest dental disparity, while hypercarnivores (felids, nimravids, many hyaenids) have the lowest dental disparity but highest cranial and mandibular disparity (excluding dentition). However, high disparity is not necessarily associated with high rates of evolution, but instead with ecological radiations. We reveal that relationships between specialization and disparity are not as simple as past research has concluded. Instead, morphological disparity results from an anatomical mosaic of evolution, where different ecologies correlate with and likely channel unique patterns/combinations of disparity per anatomical partition.

Methods
Morphological information was taken from observation and measurment of museum curated fossil and modern skeletal specimens and published datsets from scientifc literature. This was combined with molecular sequence data (nuclear and mitochondrial) for extant and recently extinct taxa downloaded form GenBank. The best partition and evolutionary models for phylogenetic analysis was determined using Stetting Stone analysis for the morphological data, while PartitionFinder 2 for the moecluar data. From these data, a total-evidence Bayesian phylogentic analysis was run in Beast. Rates of evolution and morphological disparity were then calculated from the morphological character dataset in the R Claddis package across a sample of the posterior trees in the phylogentic analysis, as well as the MCC tree.

约束是进化论中的核心概念。形态学与生态学均受功能、历史及发育因素限制，仅能占据物种理论上可利用生态位的子集。猫型总科（Feliformia）为研究表型约束提供了独特契机：多个猫型类群被认为局限于泛化的生态形态角色，而其余类群则演化出高度特化的硬食性（碎骨型）与剑齿形态。我们通过整合系统发育、形态差异度与演化速率，探究了猫型总科的演化历史。研究结果显示，不同演化支的各解剖区域形态差异度与生态位呈现镶嵌式分布模式。非超食肉动物（如灵猫科的麝猫与缟狸、马岛食蚁狸科以及已灭绝的冠犬科类群）的牙齿形态差异度最高；而超食肉动物（猫科、猎猫科、多数鬣狗科）的牙齿形态差异度最低，但颅部与下颌骨（不含齿列）的形态差异度最高。不过，高形态差异度未必对应高演化速率，反而更与生态辐射相关。本研究揭示，特化程度与形态差异度间的关联并不如既往研究所总结的那般简单。实际上，形态差异度源于演化的解剖镶嵌现象：不同生态位与各解剖分区的独特差异度模式/组合相关联，并可能对其产生约束作用。

研究方法
本研究的形态学数据源自馆藏化石与现生骨骼标本的观测与测量，以及已发表的科学文献数据集。我们将该数据与从GenBank（基因银行）下载的现生类群及新近灭绝类群的分子序列数据（核基因组与线粒体基因组）进行整合。对于形态学数据，采用Stetting Stone分析确定系统发育分析的最优分区与演化模型；对于分子数据，则使用PartitionFinder 2进行模型筛选。基于上述数据，我们在BEAST软件中开展了总证据贝叶斯系统发育分析。随后，利用R语言的Claddis软件包，基于系统发育分析的后验树样本以及最大类群置信度树，对形态学特征数据集的演化速率与形态差异度进行计算。