Phylogenetic position of a remarkable new fideliine bee from northern <scp>C</scp> hile ( <scp>H</scp> ymenoptera: <scp>M</scp> egachilidae)

Abstract Fideliine bees are an archaic group with a disjunct distribution mostly restricted to deserts of S outh A merica and S outh A frica. This group was previously thought to be more diverse in A frica than in S outh A merica, where only one genus ( N eofidelia ) comprising five species is known. Here we describe a species belonging to a second S outh A merican genus: X enofidelia colorada P acker gen. et sp.n. , from northern C hile. The species is illustrated and its phylogenetic position within M egachilidae is assessed using morphological, molecular and combined data. The 214 character morphological matrix includes 55 new characters with an additional 16 hitherto unexplored for megachilid phylogeny. The molecular dataset is based upon seven nuclear gene sequences, totalling 6439 bp, many of which are published for the first time for particular megachilid taxa. In all analyses, X enofidelia was found as sister to N eofidelia (endemic to C hile and P eru). It differs from that genus most notably in its short mouthparts, absence of a glossal rod, unmodified female metabasitarsus and an elongate and horizontal dorsal surface of the metapostnotum. Morphological and combined data support a monophyletic F ideliinae (excluding P ararhophites ), while molecular data alone failed to recover fideliine monophyly. Dating analyses suggest that X enofidelia and N eofidelia diverged 34.3–40.6 M a, indicating that N ew W orld fideliines were probably present in arid habitats of S outh A merica during the E ocene. This divergence time predates both the main orogenic events that resulted in the formation of the A ndean mountains and the origin of hyperarid conditions in the A tacama D esert; it also corresponds to a period prior to the origin of the summer rainfall area in the far north of C hile where the new genus is found. These results support the view that arid habitats have been present continuously in S outh A merica since the E ocene. This published work has been registered in ZooBank , http://zoobank.org/urn:lsid:zoobank.org:pub:EA69BB4A‐6F59‐4A15‐AB44‐2A8949E3CF8F .