Subterranean Fishes of the World

6443

2024

Integrative and Comparative Biology

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Synopsis C limat ic and geo mo rp ho log ica l chan g es durin g t he Quater nary per iod imp acte d glob a l p atterns of spe ciat ion and diversification across a wide ran g e o f taxa, bu t few studies have examined these effects on African riverin e fis h. Th e lower Con g o Riv er is an ex cellen t na tural labora t ory for under standing complex spe ciat ion and po p u lat ion diversificat io n p rocesses, as it is hydrolog ica l ly ext rem e ly dyna mic a nd re cog nize d as a cont inenta l ho tspo t o f diversi ty harbo ring m any n arrowly en- demic species. A previous study using gen om e-w ide SNP d ata hig hlig hted the importance of dynamic hydrolog ica l reg imes to the diversification and speciation in lower Con g o Riv er cichlids. How ev er, hist orical c limat e and hydrolog ica l chan g es (e.g., re duce d river di sch arge during extended dry p erio d s) h ave li kely a lso influence d ich thyofa unal diversifica tio n p rocesses in this system. The low er Con g o Riv er offers a unique o p po rtuni ty t o study c limat e-driven c hanges in river di sch arge, given the m a s- siv e v ol ume o f water fro m the entire Co n g o basin flowin g t hrough t his s h ort stret c h of t he r iv er. Here, w e, for the first time, investigate the impacts of paleoclimatic fact or s on ich thyofa unal diversifica tion in this system by inferring divergence times an d m ode lin g pattern s of g en e flow in four en demic lamprologin e cichlids, in cluding th e blin d cic hlid , La m p ro l ogus l e th ops . O ur resu lts s ugges t tha t Qua t ernary c limat e c han g es associ ated w it h r iver di sch ar g e fluctuatio ns m ay h ave imp acte d the diver- sificatio n o f spe cies a long th e system an d th e em er g ence of cryp to p hthalmic p h en otype in som e en demic spe cies. O ur study, using re duce d represen ta t ion se quencing (2RADse q), indica tes tha t the lower Congo River lamprologines emer g ed durin g the Earl y-M iddle P leis tocene t ransit ion, c haract erized as o ne o f the e art h’s m ajor clim at ic t ra nsf o rmatio n p erio ds. Mo deling results s ugges t that gene flow across po p u lat ion s and betw e en spe cies was not co nstant bu t o ccurred in temp ora l ly const raine d pu lses. We s h ow t hat t hese resul ts co rrel ate w ith gl aci al–intergl aci al fluctu a tions. The curren t hyper-diverse fish as sembla ges of the low er Con g o Riv er riv erscape li kely refle ct th e syn erg ist ic effe cts of mu lt ip le dri v ers fuelin g complex ev ol u tio nary p rocesses through time.

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