DOI: 10.5061/dryad.mn058n7
title: Cuscuta sect. Californicae (Convolvulaceae) revisited: ‘cryptic’ speciation and host range differentiation

description: Cuscuta californica complex (sensu lato, s.l.) is a western North American
 group of species in which the infrastaminal scales are reduced, making the
 morphological delimitation of species particularly challenging. A revision
 of this group was prompted by the discovery of an apparent new species
 from central California based primarily on molecular means. Prompted by
 this finding, the morphological limits of C. californica s.l. species were
 comprehensively re-evaluated through a morphometric study. DNA sequences
 from plastid (trnL–F region and rbcL), nuclear ribosomal ITS and 26S rDNA,
 as well as a low-copy nuclear pentatricopeptide repeat (PPR) gene were
 used to reconstruct evolutionary relationships among taxa. Last but not
 least, the host range of relevant taxa was determined using herbarium
 specimens. Molecular results strongly supported the new species, C.
 difficilis, which was found to be morphologically separated from C.
 brachycalyx only by subtle calyx lobe and corolla tube shape differences.
 Despite sharing some of the hosts, all the members of C. californica s.l.
 exhibited a differentiation of their host ranges. An identification key
 and description of the new species were provided together with a
 discussion on the systematics and host range of C. californica s.l..
 Hybridization, accompanied by plastid capture, was suggested as a possible
 mechanism of speciation for C. brachycalyx.
description: Supplemental Fig
 1 Neighbor-net split graph
 obtained from the AT4G01570 PPR ortholog sequences of the
 <em>Cuscuta californica</em> species complex. Major groups
 recovered and discussed in this study are highlighted and labeled. Numbers
 represent bootstrap values (1000 replicates) for some major groups (≥
 60%). Taxon accession numbers (labels) are indicated in Appendix
 1.   
 Supplemental Fig
 2 Phenogram resulted from
 the unweighted pair-group average (UPGMA) analysis using the Gower’s
 coefficient of similarity showing clearly delineated clusters of
 <em>C. difficilis</em>, <em>C. brachycalyx
 </em>and <em>C. californica</em> plus <em>C.
 occidentalis</em>. Cophenetic correlation coefficient = 0.8659. For
 details on the specimens used see Appendix 1.   
 Supplemental Fig
 3 Family level host range
 in <em>Cuscuta californica</em> s.l. visualized as a bipartite
 directed network. Five <em>Cuscuta</em> taxa nodes represented
 as triangles are connected with the corresponding nodes (circles) of their
 family hosts. The frequency of particular
 <em>Cuscuta</em>-host family associations is indicated by the
 proportionally thickened lines (edges) using the host-frequency indicator
 (HFI). The number of edges shared by <em>Cuscuta</em> taxa and
 their host families indicates the amount of overlap or separation of the
 host ranges.   
 Supplemental Fig
 4 Genus level host range
 in <em>Cuscuta californica</em> s.l. visualized as a bipartite
 directed network. Five <em>Cuscuta</em> taxa nodes represented
 as triangles are connected with the corresponding nodes (circles) of their
 family hosts. The frequency of particular
 <em>Cuscuta</em>-host genus associations is indicated by the
 proportionally thickened lines (edges) using the host-frequency indicator
 (HFI). The number of edges shared by <em>Cuscuta</em> taxa and
 their host genus indicates the amount of overlap or separation of the host
 ranges.   
 Supplemental Fig
 5 Supplemental Fig. S5.
 UPGMA dendrogram based on the species/variety level host-frequency
 indicator matrix and using Euclidian similarity index. Cophenetic
 correlation coefficient = 0.9977.   Costea_cryptic_speciation_morphometric_matrix.xlsx Data used in the morphometric analysis. For characters details see Table 1 in the paper. For specimen details see Appendix one in the article.   Costea_cryptic_speciation_host_matrices.xlsx Containes the compiled host data; host data matrices and HFI matrices.
description: Please see "materials and methods" within the
 paper.