了解表型可塑性和由此产生的形态差异的根本原因是进化研究的关键主题之一。现存和化石黑色素的表型可塑性已被广泛记录。然而,千年决议,来自具有地方性的小型水生栖息地的过时记录很少。温泉喂养的Peea湖是一个冰河时代的避难所,拥有独特的特有温水动物区系。亚化石黑色素显示出令人难以置信的形态变异,从光滑到龙骨,细长到带肋,肩负的形式。许多形态类型被认为是单个类群,从光滑的细长到有肋的流畅的序列,肩带类型。这项研究对亚化石黑色素进行了广泛的形态计量学分析(约3500个标本)来自具有独立时间顺序的分层样本。目的是分离形态类型,以研究时间形态差异。我们的结果挑战了广泛接受的假设,该假设提出了肩,压缩,有肋的外壳通过两步过程从光滑细长的纺锤形的外壳。相反,这表明亚化石壳属于整个可用地层数据中存在的两个不同的分类单元。形状变化的主要成分,形状球状,和壳盘绕似乎与测速有关。肋条,条纹,龙骨随机出现。高螺旋状的纺锤形形式被认为代表了Microcolpiadaudebartiihazayi的标本。笨重的低螺旋状和肩状标本代表Mi的表型。ParreyssiiParreyssii.湖泊历史早期形态类型的集体和随机分布也驳斥了将细长形式连续转化为压缩形式的想法,肩负的。而是指向多个事件和环境刺激触发发展。黑色素出现在晚期冰河层,Theodoxusprevostianus更喜欢高于23°C的温度,这可能表明在较冷的水域中存在热水微生境。
Understanding the underlying reasons for phenotypic plasticity and resulting morphological disparity is one of the key topics of evolutionary research. The phenotypic plasticity of extant and fossil melanopsids has been widely documented. Yet millennial-resolution, well-dated records from small aquatic habitats harboring endemics are scarce. The thermal spring-fed Lake Pețea is an ice age refugia harboring a unique endemic warm-water fauna. Subfossil melanopsids display incredible morphological variability from smooth to keeled, elongated to ribbed, shouldered forms. Numerous morphotypes have been considered as individual taxa with a fluent succession from the smooth elongated to the ribbed, shouldered types. This
study presents an extensive morphometric analysis of subfossil melanopsids (ca. 3500 specimens) derived from stratified samples with an independent chronology. The aim was to separate morphotypes for investigations of temporal morphological disparity. Our results challenge the widely accepted hypothesis that proposes the evolution of shouldered, compressed, ribbed shells through a two-step process from smooth elongated spindle-shaped shells. Instead, it suggests that the subfossil shells belong to two distinct taxa present throughout the available stratigraphic data. The main components of shape variation, shape globularity, and shell coiling seem allometry-related. Ribs, striation, and keels appear randomly. High-spired spindle-shaped forms were considered to represent specimens of Microcolpia daudebartii hazayi. Bulkier low-spired and shouldered specimens represent phenotypes of Mi. parreyssii parreyssii. The collective and random distribution of morphotypes from the early stages of the lake\'s history also refutes the idea of a continuous transformation of the elongated forms into compressed, shouldered ones. Rather points to multiple events and environmental stimuli triggering development. Melanopsids appear in Late Glacial horizons, with Theodoxus prevostianus preferring temperatures above 23°C which may indicate the subordinate presence of hot water microhabitats in cooler waters.