Developmental Integrative Biology Research Group, Department of Biological Sciences, University of North Texas, Denton, TX, 76203, USA.
Multiscale Biology, Johann-Friedrich-Blumenbach Institut für Zoologie und Anthropologie, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077, Göttingen, Germany.
Cladistics. 2023 Jun;39(3):240-248. doi: 10.1111/cla.12526. Epub 2023 Feb 4.
In the field of phylogenetic systematics, the terms homology and homologue and their relationship to cladistic terms such as character, character state, synapomorphy and symplesiomorphy, as well as their relationships to each other, have been and are still discussed frequently. A recent re-emergence of concepts of homology/homologue free of any reference to explanatory hypotheses prompted us to explore these concepts and their relationships to each other as well as to the concept of morpheme, as introduced recently. All concepts are examined with regard to their ontological status and their bearing in the epistemological process in morphology and phylogenetic systematics. To us, morphemes, homologues and in partem character states refer to things (concrete objects in the ontological sense). However, although morphemes are exclusively descriptive, the latter two represent objects of causal explanations. Homologue always refers to the things themselves, yet a character state also can be a property or the absence of a thing. In this context, a character as a transformation series of character states does not represent a thing but a natural kind. Character states of one character are connected by homology relationships, i.e. common descent. Synapomorphy and symplesiomorphy represent different states of a single transformation series. A nonexplanatory, purely descriptive, concept of homologues is contradictory to its original as well as the post-Darwinian, evolutionary, concept which refers to causal relationships between parts of organisms and their correspondences in the archetype or ancestor, respectively. Character states, homologues and synapomorphies/symplesiomorphies can only be approximated in the form of hypotheses. We argue that the high value of the concept of homology and its related concepts for evolutionary biology should be maintained by acknowledging their explanatory nature and that dilution with nonexplanatory (even idealistic) definitions should be avoided.
在系统发育系统学领域，同源和同源物这两个术语及其与分支学术语（如特征、特征状态、同源特征和同形特征）的关系，以及它们彼此之间的关系，一直并且仍然在频繁讨论。最近，出现了一种概念，即同源/同源物的概念，无需参考解释性假设，这促使我们探索这些概念及其相互关系，以及最近引入的形态学和系统发育系统学中的形态概念。所有概念都从本体论地位以及在形态学和系统发育系统学的认识论过程中的作用进行了检查。对我们来说，语素、同源物和部分特征状态指的是事物（本体论意义上的具体对象）。然而，尽管语素完全是描述性的，但后两者代表因果解释的对象。同源物始终指的是事物本身，但特征状态也可以是事物的属性或缺失。在这种情况下，作为特征状态的特征不是事物本身，而是一种自然种类。一个特征的特征状态通过同源关系连接，即共同祖先。同源特征和同形特征代表单个转换系列的不同状态。非解释性的、纯粹描述性的同源物概念与其原始概念以及后达尔文进化概念相矛盾，后达尔文进化概念分别指的是生物体各部分之间的因果关系及其在原型或祖先中的对应关系。特征状态、同源物和同源特征/同形特征只能通过假设来近似。我们认为，应该通过承认其解释性质来保持同源概念及其相关概念对进化生物学的高价值，并且应该避免用非解释性（甚至是唯心主义的）定义来稀释它们。
