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<p>An accurate taxonomic characterization of species diversity is vital for ecological and evolutionary research. Thus, it is necessary to establish species limits based on different sources of evidence. We examined variation of the mitochondrial COI gene and the nuclear ITS1 marker of <i>Keratella americana</i> f. <i>hispida</i> to determine whether this morphological variant can be described as a distinct species from the <i>K. americana </i>sensu stricto. We conducted three methods of species delimitation (ABGD, ASAP, PTP-ML, and PTP-B) to identify Evolutionary Significant Units (ESUs) corresponding to species. We also performed morphological analyses including detailed observations using a scanning electron microscope to examine the tiny spinules in the <i>hispida</i> form. Our results indicated that <i>K. americana</i> f. <i>hispida</i> is only a morphological variant of the <i>K. americana</i>. Average genetic divergences within the <i>Keratella americana</i> lineage were 1.3% for COI and 0.1% for ITS1 marker. Morphologically, the spinules in <i>K. americana</i> f. <i>hispida</i> have a peculiar flower-like shape, although the function of these structures remains unknown. We speculate that the presence of predators in the environment may induce the development of these spinules, given that the specimens were collected in a complex tropical environment with high diversity of zooplankton species.</p>

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Keratella americana f. hispida a little-known morphological variant of Keratella americana Carlin, 1943 (Rotifera, Monogononta, Brachionidae)

  • 期刊论文

  • 发表日期：

    2026年7月28日

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  • Alma E. García-Morales,
  • Manuel Elías Gutiérrez

摘要

An accurate taxonomic characterization of species diversity is vital for ecological and evolutionary research. Thus, it is necessary to establish species limits based on different sources of evidence. We examined variation of the mitochondrial COI gene and the nuclear ITS1 marker of Keratella americana f. hispida to determine whether this morphological variant can be described as a distinct species from the K. americana sensu stricto. We conducted three methods of species delimitation (ABGD, ASAP, PTP-ML, and PTP-B) to identify Evolutionary Significant Units (ESUs) corresponding to species. We also performed morphological analyses including detailed observations using a scanning electron microscope to examine the tiny spinules in the hispida form. Our results indicated that K. americana f. hispida is only a morphological variant of the K. americana. Average genetic divergences within the Keratella americana lineage were 1.3% for COI and 0.1% for ITS1 marker. Morphologically, the spinules in K. americana f. hispida have a peculiar flower-like shape, although the function of these structures remains unknown. We speculate that the presence of predators in the environment may induce the development of these spinules, given that the specimens were collected in a complex tropical environment with high diversity of zooplankton species.