Morphological and molecular systematic investigation of Laurencia karachiana sp. nov. (Ceramiales, Rhodophyta) from Karachi, Pakistan

Abstract

Laurencia karachiana sp. nov. is described from the Karachi coast of Pakistan, based on rbcL and COI-5P genes sequences. The molecular analyses for both markers positioned L. karachiana within Laurencia sensu stricto and it possesses all vegetative and reproductive structures typical of the genus. Laurencia karachiana grouped with Laurencia sp. from Sri Lanka for both markers. The genetic divergence between these taxa for rbcL was only 0.27%, whereas for COI-5P was much higher, 2.7%. The latter is within ranges of interspecific divergence for Laurencia s.s. The discrepancy of divergence between these markers and the lack of description and illustrations of Laurencia sp. from Sri Lanka for comparison leave the identity of Laurencia sp. as an open question. The rbcL phylogeny resolved L. karachiana and Laurencia sp. as sister to a subclade formed by sequences of Laurencia pumila and L. pumila var. dehoopiensis from South Africa, diverging by 1.7–1.8%. This genetic divergence and also morphological differences observed support the recognition of L. karachiana as a novel species. Our finding shows that this complex from Pakistan requires major revision, because its diversity is likely underestimated.