Allopatric differentiation in theMarcusenius macrolepidotusspecies complex in southern and eastern Africa: the resurrection ofM. pongolensisandM. angolensis, and the description of two new species (Mormyridae, Teleostei)

Abstract

Allopatric differentiation in the AbstractWe critically compared local populations of the bulldog fish, Marcusenius macrolepidotus (Peters 1852), from different watersheds, from the furthest south (28u South, South Africa) to the Equator in Kenya. We ascertained allopatric differentiation from topotypical M. macrolepidotus from the Lower Zambezi River (Mozambique) in morphology, electric organ discharges, and molecular genetics for: (1) samples from the Okavango and Upper Zambezi Systems (Botswana and Namibia), (2) samples from South Africa's rivers draining into the Indian Ocean, and (3) samples from the East African Tana River (Kenya). Significant genetic distances in the mitochondrial cytochrome b gene and differing ISSR-PCR profiles corroborate differentiation between the four taxa. We resurrect M. pongolensis (Fowler, 1934) for South Africa (sample 2), and M. angolensis (Boulenger, 1905) for the Quanza River/Angola. We recognize M. altisambesi sp. n. for the Upper Zambezi/Okavango specimens (sample 1), and M. devosi sp. n. for those from Kenya (sample 3).

Female choice by electric pulse duration: attractiveness of the males'communication signal assessed by female bulldog fish,Marcusenius pongolensis(Mormyridae, Teleostei)

“…Kramer, 23-25 September 1993: one male, Sabie-Sand River at Londolozi, 24°47Ј31ЉS, 31°31Ј32ЉE; five males, Sabie River above Hazyview, 25°02ЈS, 31°00ЈE; one male, Sabie River just above Hazyview, 25°01Ј48ЉS, 31°01Ј21ЉE; further details are given elsewhere (Kramer et al, 2007)]. Recordings from the other 18 males originating from the Crocodile River (see above) were made in the laboratory (see Kramer et al, 2007). The two inter-discharge interval (IDI) patterns used for driving the output of playback pulses were also recorded from two captive Crocodile River males.…”

“…All fish used in this study were considered to be Marcusenius pongolensis (Fowler, 1934), a recently resurrected species, the synonymisation of which with M. macrolepidotus (traditionally referred to as the bulldog fish) was recognised as unjustified (Kramer et al, 2007 Another seven experimental subjects were laboratory-raised descendants of fish sampled from the Crocodile River (E5-E11; SL 9.5-11.4·cm at the time of the tests; locality as given above). For playback stimulation we used the EODs of 25 different, wildcaught males, seven of which had been recorded in the field near the site of their capture [collected by P. Skelton and B.…”

“…For playback stimulation we used the EODs of 25 different, wildcaught males, seven of which had been recorded in the field near the site of their capture [collected by P. Skelton and B. Kramer, 23-25 September 1993: one male, Sabie-Sand River at Londolozi, 24°47Ј31ЉS, 31°31Ј32ЉE; five males, Sabie River above Hazyview, 25°02ЈS, 31°00ЈE; one male, Sabie River just above Hazyview, 25°01Ј48ЉS, 31°01Ј21ЉE; further details are given elsewhere (Kramer et al, 2007)]. Recordings from the other 18 males originating from the Crocodile River (see above) were made in the laboratory (see Kramer et al, 2007).…”

“…In adult males of the South African bulldog fish, Marcusenius pongolensis, EOD pulse duration increases with standard length (SL; measured from tip of upper jaw to midbase of caudal fin) over lifetime (Kramer et al, 2007); this is not found in females. Male EOD pulse duration therefore seems to signal strength and fighting ability to conspecific contenders for territories or access to females, a conclusion supported by a study of male-male encounters in a territorial conflict setting, both with live neighbours and simulated ones by electrical playback stimulation (Hanika and Kramer, 2005) (Hanika and Kramer, in press).…”

“…All EODs were biphasic short pulses with a head-positive first phase followed by a negative one, as is common in the genus Marcusenius, and described in more detail elsewhere (Kramer et al, 2007). Custom-made routines programmed in the package FAMOS (imc, Berlin) measured EOD pulse duration using an amplitude criterion of ±5% of the peak amplitude P of an EOD.…”