Presented during the 17h Annual Sahelo-Saharan Interest Group Meeting organized by the NGO Sahara Conservation Fund in Senegal, from 4 to 6 May 2017. The Sahara Conservation Fund (SCF) gathers every year about a hundred people who are interested in the field of Sahelo-Saharan species conservation.

1. 17th Annual Sahelo-Saharan Interest Group Meeting
2 days of talks on biodiversity conservation in the Sahara and in the Sahel
Small Sahelo-Saharan mammals evolution : case study of rodents of the genus
Gerbillus
Arame NDIAYE et al. , Researcher– Institut de Recherche pour le Développement
May 4 – 6, 2017

2. Importance of evolutionary biology in
understanding small Saharo-Sahelian mammals
evolution: case study of rodents of the genus
Gerbillus (Rodentia: Muridae)
Laurent GRANJON, Gauthier DOBIGNY, Pascale CHEVRET & Arame NDIAYE

3. Considered as one of the most speciose
genus within rodents, with no less than
fifty recognized species.
Order
Rodentia
sub-Order
Myomorpha
Family
Muridae
sub-Family
Gerbillinae
Genus Gerbillus &
Dipodillus
(sensu Musser &
Carleton 2005)
Genus Gerbillus (incl. Dipodillus)

4. Diagnostic criteria
Bulky and voluminous eyes
Soft coat with back /
belly line (white)
LTC < LQ
Plantar soles
+/- hairy
(intermediary)
Bare foot soles
Hairy plantar soles
Hair tail with terminal
brush +/- supplied

5. Terrestrial and nocturnal, mainly
granivorous, they live in burrows
comprising galleries found in sandy to
more indurated substrates, or (rarely) in
holes of rocky habitats
Elements of ecology
Include species that are potentially harmful to
- dry crops (G. nigeriae) or market gardens
(G. campestris)
- or potentially reservoirs of pathogens
that are transmissible to humans or
livestock

6. The genus Gerbillus is widespread in arid to semiarid Africa and Asia via the
Arabian Peninsula
6
42
4
6 asian species
with only 1 endemic*
42 african species
with 27 endemics*
4 afro-asian species
Distribution
* Only known from a given locality or limited region

7. Several attempted inventories of
such species
Lay (1983): 62 species (all in Gerbillus)
Ellerman (1941): 77 species (42 Gerbillus
- 35 Dipodillus)
Musser and Carleton (2005): 51 species
(38 Gerbillus - 13 Dipodillus)
Two, or even 3 distinct genera
(Dipodillus, Gerbillus ss and Monodia)
vs 1 alone (Gerbillus)
Characters used:
- Body / Cranial Measurements
- Size / shape of the tympanic bullae
Hairiness of plantar soles
Dental morphology (especially upper 1 molar)
Shape of the mandible
Different divisions of the
genus proposed
Gerbillus, Dipodillus
Hendecapleura and Petteromys
proposed as subgenera of Gerbillus
or Dipodillus
Taxonomy

8. Difficulty in accounting for real
biodiversity in this genus
Use of other methods such as molecular and
cytogenetic tools Integrative Taxonomy
Identification of species
based essentially on
morphological analysis
G. henleyi
But very conservative morphology…
G. pyramidum
Taxonomy
Case of sibling species
Under estimate of biodiversity
Case of polymorphic species
Overestimating diversity
+ Difficulty in finding diagnostic characters of subsets representing real evolutionary
units

9. Molecular phylogeny of significant species sampling (N = 21):
Usuals methods like DNA extraction (Qiagen), PCR of cytochrome B (1140bp)
and IRBP (1272 bp) and Sanger sequencing
89 samples from 71 localities and 16
countries (+ outgroups)
Ndiaye et al. (2016)

10. Mains molecular phylogeny results
cyt b IRBP
Clade A=
Hendecapleura
Clade C =
Gerbillus
Clade D = Monodia
Clade B =
Dipodillus
Clade D = Monodia

11. subgenus
Hendecapleura
subgenus
Dipodillus
subgenus
Gerbillus
subgenus Monodia
Combined analyse (cytb + IRBP) with taxonomic hypotheses
G. poecilops, G. henleyi,
G. nanus, G. amoenus
G. rupicola, G. campestris
G. dasyurus, G. simoni
G. nancillus
G. cheesmani, G. gerbillus
G. andersoni, G. nigeriae, G.
pyramidum, G. floweri, G.
latastei, G. hesperinus, G.
hoogstraali, G. occiduus, G.
tarabuli, Gerbillus sp.1 &
Gerbillus sp2
Outgroup

12. Divergence
Gerbillinae /
Deomyinae
Divergence Acomys / Lophuromys
1st mention of
Gerbilliscus
Divergence Gerbillus /
Sekeetamys
Molecular datation using fossils calibration
Estimated dates:
Divergence Sekeetamys-
Gerbillus: - 6,5MYA
Miocène. Plio. Pleist.
subgenus
Hendecapleura
subgenus
Gerbillus
subgenus Monodia
subgenus
Dipodillus
Emergence of Hendecapleura:
- 5,1 MYA
Emergence of Gerbillus: -
4,1 MYA
Emergence of Dipodillus: -
3,6 MYA
Emergence of mostly
Gerbillus species:
Pleistocène (except. G.
poecilops & G. campestris)
Outgroups

13. Reconstruction of ancestral distribution areas
subgenus
Gerbillus
subgenus
Dipodillus
subgenus
Monodia
subgenus
Hendecapleura
Outgroups
Evolutionary history of
subfamily (Gerbillinae)
and Gerbillus genus
mainly inAfrica
very few dispersions
events in Gerbillus ,
probably from Africa to
Asia (G. cheesmani, G.
nanus, G. poecilops)

14. The IUCN Red List of Threatened Species. Version 2016-2.
<www.iucnredlist.org>. Downloaded on 20 November 2016
How this will help us to better understand G. nanus – G. amoenus
evolution of distribution area?
G. nanus
sibling species
G. amoenus

15. Specimens from
Israël and
Pakistan
Specimens from
Mauritania, Mali
and Lybia
G. nanus
G. amoenus
1st Results of complete cytochrome b sequences (Ndiaye et al. 2013) obtained
from fresh samples
K2P genetic distance between 2
clades of « G. nanus » (sensu lato)
= 0,065
MLtree
➔ hypothesis of an asian species (G. nanus) and an african species (G. amoenus?)
Africa
Asia

16. Afghanistan*
Egypte*
Niger
Mauritanie
Testing previous hypothesis using partial cytochrome b sequences of old
specimen collection (Field Museum, Chicago; Ndiaye et al. 2016b)
Gerbillus nanus
Gerbillus
amoenus
A sampling of 6 species including 6 specimens of G. amoenus (From Egypt)
and
4 specimens of G. nanus (from Pakistan and d’Afghanistan) collected from 1918 and 1965
Africa
Israël
Pakistan*
Asia

17. G. nanus G. amoenus
G. amoenus
G. nanus
Molecular data suggested biogeographical revisions
G. amoenus and G. nanus = vicariant species on both sides of the red Sea,
differentiated since 1,4 +/- 0,7MA (through Sinaï/Negev from West to East)
But a question about possible synonymy of G. garamantis (The « Algerian » gerbil, 2n = 54,
described from Ouargla) with G. amoenus (2n = 52): If synonymy, G. garamantis should be the
correct name (anteriority rule); if not, both species are represented in North Africa.

18. Sibling species find in Senegal due to Integrative taxonomy
G. henleyi known to occur in Senegal since 1980
BUT Samples firstly identify like G. henleyi were too different (molecular)
Use of various methods sampling small Gerbillus with hairless plantar soles
(subgenus Hendecapleura) from sahelien area
G. henleyi
G. nancillus
2n = 52
2n = 56
Ndiaye et al. 2014

19. G. henleyi G. nancillus
! Suggesting (1) the extension of the distribution area and (2) one more Gerbillus
species in Senegal small mammals diversity
A: PCAon body
measurements
B: PCA on skull
measurements
C: DA on skull
measurements

20. Conclusions
• Gerbillus = very interesting group to study arid areas
• Incomplete Systematic which is important and preliminary
to all other studies (ecology, physiology, biogeography…)
• Importance of good sampling for better interpretation
• Importance to combine methods for better diagnosis
from collections/Museum withspecimens
methods ==> Very important to complete
• Use of
adequate
sampling

21. Perspectives
Why are we doing all this work upstream…?
• like biological invasions in WestAfrica
• with several biological pests of cereal crops (G.
nigeriae) or market gardeners (Tuta absoluta) with
consequences in Food security, trade… ==> JEAI-
IBAO
• Describe and better understand the modalities of
these bio-invasions ==> can affect real biodiversity
in Saharo-sahelian area
More applied Sciences !!!