Multilocus Data Analysis Reveal the Diversity of Cryptic Species in the Tillandsia ionantha (Bromeliaceae: Tillansiodeae) Complex

Abstract

Independent evolutionary lineages or species that lack phenotypic variation as an operative criterion for their delimitation are known as cryptic species. However, these have been delimited using other data sources and analysis. The aims of this study are: (1) to evaluate the divergence of the populations of the T. ionantha complex; and (2) to delimit the species using multilocus data, phylogenetic analysis and the coalescent model. Phylogenetic analyses, genetic diversity and population structure, and isolation by distance analysis were performed. A multispecies coalescent analysis to delimit the species was conducted. Phylogenetic analysis showed that T. ionantha is polyphyletic composed of eight evolutionary lineages. Haplotype distribution and genetic differentiation analysis detected strong population structure and high values of genetic differentiation among populations. The positive correlation between genetic differences with geographic distance indicate that the populations are evolving under the model of isolation by distance. The coalescent multispecies analysis performed with starBEAST supports the recognition of eight lineages as different species. Only three out of the eight species have morphological characters good enough to recognize them as different species, while five of them are cryptic species. Tillandsia scaposa and T. vanhyningii are corroborated as independent lineages, and T. ionantha var. stricta changed status to the species level.

Keywords: Tillandsia ramireziana; Tillandsia vanhyningii; allopatric speciation; coalescent species delimitation; cryptic species.

Figure 1

Phylogenetic tree estimated with Bayesian Inference using three cpDNA markers; PPB values ≥ 0.95 on the branches; Bootstrap values ≥ 50 below the branches. The collapsed and colored clades represent each of the eight lineages within the T. ionantha complex. Uncolored branch terminals (taxa) represent outgroup species.

Figure 2

Phylogenetic tree estimated with Bayesian Inference using PHYC; PPB values ≥ 0.95 on the branches; Bootstrap values ≥ 50 below the branches. The collapsed and colored clades represent each of the eight lineages within the T. ionantha complex. Uncolored branch terminals represent outgroup species.

Figure 3

Evolutionary relationships between haplotypes, each set of haplotypes of the same color represents the same lineage. (A) Geographic distribution pattern of the haplotypes for both sets of markers. (B) Reconstruction of the haplotype network of the markers rps16-trnQ and rpl16-rps3 using the TCS Network model. (C) Reconstruction of the PHYC marker haplotype network using the TCS network model.

Figure 4

F_ST values for pairwise comparison between populations of T. ionantha complex. (A) F_ST pairwise of cpDNA and (B) F_ST pairwise of nDNA.

Figure 5

Maximum clade credibility tree of the Tillandsia ionantha species aggregate, along with outgroup taxa, resulting from the multilocus coalescent analyses in STACEY (Beast2). Values above branches are posterior probabilities of clade support. The colors of the perimeter of the photographs correspond to the colors of each of the evolutionary lineages of the minimal clusters tree.

Figure 6

Geographic distribution of the taxa of the T. ionantha complex and populations sampled (numbers 1–19). Populations 1, 2, 16, 18 and 19 represent the type localities of T. scaposa, T. vanhyningii, T. ionantha var. zebrina, T. ionantha var. stricta and T. ionantha var. maxima respectively.

Figure 7

Geographical distribution of Tillandsia ramireziana (black squares), Tillandsia scaposa (yellow squares) and Tillandsia vanhyningii (red squares).