Mascarenes islands : biogeographical features

Habitat diversity (Reunion island)

Endemism and geographical origin of biotas

Biological Conservation issues

dominique.strasberg@univ-reunion.fr

blog.univ-reunion.fr/demin

Photo H. Douris. Parc National

11 LECTURERS or PROFESSORS

20 PERMANENT SEARCHERS

45 TECHNICIANS

18 PhD

16 Postdoc

15 Permanent staff in crop biosecurity

and innovation

umr-pvbmt.cirad.fr

•  Mascarenes islands : Reunion, Mauritius and

Rodrigues

•  Home of DODO, symbol of human caused

extinction and biodiversty loss

21°S 55.5°E

The fauna experienced a HIGH EXTINCTION RATE

Despite a very RECENT human settlement : •  Among 60 native birds sp. 2/3 extinct on Mascarenes Islands

J. Hume JJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJ...................................................... HHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuummmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee Paintings J. Hume

Native forest cover at Mauritius in 2015 : less than 2% is left

Main driver of extinction : habitat

transformation?

1988

Extinction rate of Mauritius land snails 44%

(86 endemic species)

Plegma duponti Gibbus lyonetianus

Tropidophora carinata

Photos V. Florens

Madagascar biodiversity hotspot

Marine and Terrestrial Biodiversity Hotspot

Number of endemic species / km2 is high

Mascarenes harbor 25 % of their original cover

http://runemerge.univ-reunion.fr

ANR-06-BDIV-0002

VOLCANIC ORIGIN, Never connected to land mass

© Aline Peltier © observatoire © observatoire

considered as an analog to HAWAII

Geographical features

PRESENT

FEATURES

Réunion Mauritius Rodrigues

AREA 2512 km2 1865 km2 110 km2

MAX

ELEVATION

3070 m 828 m 398 m

AGE 2.1 Myrs 7.8 Myrs 1.5 Myrs

3 ISLANDS

GEOLOGICALY YOUNG

(lava flows on surface even

younger, 0.2 M)

Geographic

isolation

across time?

Geography when sea level

was 135 m BPSL

3,800 km

420 km

Habitat

Diversity Photo H. Douris.

Parc National

Past and

present

native

vegetation

20 BHU

30 % is left

Habitat diversity

on Reunion Island

Strasberg, Rouget, Richardson et al 2005

Semi-dry forest

(Coastal Palm

forest)

Average annual Tp: 23°C

Precipitation: coast = 500- 1000 mm/year

Trees (7-20m) and lianas: 32

Small trees (1-6m): 32

Terrestrial herbs: 14

Epiphytes: 22 800

100

750 750

Lowland

rainforest

Average annual Tp: 23-24°C

Precipitation: coast = 1500 mm/year

> 10 m in the E

Trees (7-20m) and lianas: 35

Small trees (1-6m): 18

Terrestrial herbs: 10

Epiphytes: 37

Hemiparasites: <1 800

1100

750

Dense mountain cloud forest

Average annual Tp: 17°C

Precipitation: East around 4000 mm/year

W around 1500 mm

ETP reduced + Fog interception

Trees (7-15m) and lianas: 26

Small trees (1-6m): 20

Terrestrial herbs: 19

Epiphytes: 35

Hemiparasites: <1

800

1100

2000

1900

Photo S. Baret

Disa borbonica

Hypericum lanceolatum

Stoebe passerinoides

Ericaceae , Asteraceae

Subalpine scrubland : grasslands and heathlands

2000

1900

3070

Average annual Tp: 10.9°C

Precipitation: East > 3000 mm/year

W from 1500 to 2500mm

No trees

Dominance by Shrubs

Terrestrial herbs: from 10 to 30%

Habitat

diversity

a very rugged

topography

erosion records

Photo H. Douris. Parc National

200

750 800

1100

2000

1900

3070 m NW

SE

Trade

winds

Lowland rainforest

Tropical mountain cloud forest

Subalpine vegetation

Semi-dry forest

a strong Elevation gradient 0-3070 m a.s.l.

Habitat Zonation, (Cadet 1977)

AVERAGE

RAINFALL

ranges

from 0.5 m to 12 m

Which mechanisms control biodiversity patterns along elevation gradients, accross islands?

ERANET Biome funding, Conseil Regional, ANR

French Polynesia

Guadaloupe

Canary Is.

Açores

La Reunion

Madagascar

Kenya Kenynynynynynynynynynynynynynynynynynynynynynynynynynynynynynynynynynynya

Ah Peng et al 2015 moveclim.blogspot.com

moeclim.blogspot.com

MOVECLIM : montane vegetation as listening posts for climate

change

20

Area: 400.6 km2

Top: 1,021 m

Pop.: 56,437

(141 /km2)

Geol. age: 1 MY

Area: 706 km2

Top: 2,426 m

Pop.: 21,145

(30/km2)

Geol. age: 3 MY

Area: 2,511 km2

Top: 3,070 m

Pop.: 840,974

(330/km2)

Geol. age: 2 MY

Area: 581,540 km2

Top: 2,876 m

Pop.: 22,005,222

(35.2/km2)

Geol. age: 88 MY

Area: 447,0 km2

Top: 2,350 m

Pop.: 14,806

(35.3 /km2)

Geol. age: 0,25 MY

Endemism and Geographical origin of native biotas

Endemism distribution among taxa

Thébaud, Warren, Strasberg & Cheke 2009

« DISHARMONIC » vertebrate fauna with no terrestrial

mammals and no amphibians

Cheke & Hume 2008

M. Attié

Main AFRICAN Origin,

+ EASTERN Origin implying

Long distance dispersal : Acacia heterophylla

And

several lineages of

plants, birds (Dodo), bats,

skinks, beetles, ….

Leroux et al. 2014

New Phytol.

Crédits Photo : T. Pezet, F. Martos et J.F.

Bègue

How biodiversity has built up?

/ Anagenesis

Ex : orchid species richness (Micheneau et al. 2008)

Daisy trees (Psiadia)

diversified into 26

endemic species

From 2 independent

colonisation events

1 Reunion clade (older)

1 Mauritian clade

> = to Madagascar

Cladogenesis and diversification

Strijk, Noyes, Strasberg et al. 2012

Major Gaps in Systematic studies

And we know very few about processes!

speciation of orchids (Mallet et al. 2015)

Zosterops diversification

(Bertrand, Mila, Thébaud et al. 2014)

zoboscience sites.google

Biological Conservation issues

The National Park covers 40% of Reunion area

+ World heritage site

Involving regional stakeholders in native Mascarenes habitats preservation

Most impacting/abundant

introduced vertebrates in

Reunion native habitats

Main threat from biological invasions :

65 vertebrates species introduced to Reunion

25 invaders

Photos V. Florens

FIRE FEQUENCY

FRAGMENTATION

ROAD BUILDING

promoted by landuse

and disturbances regime

changes

Alien plants invasions

In 250 yrs

More than 2500 introduced

835 naturalized

132 invasive

Baret et al. 2008

CBNM. 2014

Rubus alceifolius recently « eradicated » from

the lowlands / biocontrol

Rosaceae

2000 1900

750

Research programs and biocontrol conducted

on one Bramble species

Cirad Réunion

Psidium cattleianum

Syzygium jambos STRAWBERRY GUAVA the worst « transformer » in the

Mascarenes

the most appreciated fruit at Reunion

Casuarina equisetifolia invading recent lava flows

altering ecosystem functioning

Potgieter et al 2014

Fuchsia boliviana

F. x exoniensis

F. magellanica Mountain cloud forest

Photo S. Baret

NEW INVASIVE SPECIES

RISK ANALYSIS

TO PREVENT INTRODUCTIONS,

Photo JM. Probst

Active Invasive species management in protected areas at Mauritius

Lack of native community recovery

)

Photo V. Florens

Breakdown of

plant x animal interactions

Rewilding programs (?)

Photo J. Hume, B. Warren

Thanks for your attention!