NearComplete Extinction of Native Small Mammal Fauna 25 Years After Forest Fragmentation

To identify the Rattus species dominating islands in the reservoir, we collected tissue samples from multiple sites in the reservoir; all individuals were identified as Rattus tiomanicus

www.sciencemag.org/content/341/6153/1508/suppl/DC1

Supplementary Materials for

Near-Complete Extinction of Native Small Mammal Fauna 25 Years

After Forest Fragmentation

*Corresponding author E-mail: lggibson@nus.edu.sg (L.G.); fhe@mail.sysu.edu.cn (F.H.);

dbsbdp@nus.edu.sg (D.P.B.)

Published 27 September 2013, Science 341, 1508 (2013)

DOI: 10.1126/science.1240495

This PDF file includes:

Materials and Methods

Figs S1 to S3

Tables S1 to S3

References (31–38)

Supplementary Materials

Materials and Methods: We surveyed islands in Chiew Larn Reservoir in Surat Thani province,

Thailand 5-7 years following isolation (1992-1994) and 25-26 years following isolation (2012-2013) We selected islands of various sizes (< 1 to > 50 ha) in remote parts of the reservoir, mostly in the upper reservoir where there are more islands and where there is little human

disturbance We did not survey islands where there was any human presence The same 12 islands were sampled during both time periods, but most were small islands (Table 1) To ensure findings from the large islands were representative, we also sampled four additional large islands

in the most recent surveys

We used trapping transects to survey small mammal communities Sampling effort was

small islands (~ 1 ha), 4-5 transects on medium islands (~ 10-25 ha), and approximately 8-10

transects on large islands (~ 50 ha) (31) Consequently, larger islands were sampled more

intensively than smaller islands on an absolute basis, but less intensively per unit area Trapping transects spanned 135 m In each transect, 10 Tomahawk live traps were placed on the ground at every 15 m, and 4 Sherman live traps were mounted on lianas or fallen trees 0.5-2 m above the ground every 45 m Traps were baited with a mixture of bananas and coconut pieces covered in peanut butter Each island was sampled for seven consecutive days and traps were checked before 11:00 am to ensure the safety of trapped animals

Captured animals were handled briefly for identification, marked using ear tags, and released unharmed within a few minutes Species were identified using a regional guidebook

(24) To identify the Rattus species dominating islands in the reservoir, we collected tissue samples from multiple sites in the reservoir; all individuals were identified as Rattus tiomanicus

by J-F Cosson using genetic markers

To compare the number of species on islands between different sampling periods, we applied a generalized linear model with a gamma error distribution and log-link function to account for the non-normal nature of our response variable and for predictor heteroscedasticity

We compared and ranked models using Akaike’s information criterion corrected for small

via its percent deviance explained (%DE)

We developed an island biogeographic model to predict the number of species on forest fragments after time since isolation Before isolation, the equilibrium number of species on an

island is assumed to follow a power-law model (34)

island, and c and z are constants Simple power-law species-area relationships generally perform best across datasets (35)

The theory of island biogeography postulates that the change in the number of species on

an island would be

new species immigrating to an island during the elapsed time interval (t, t+1), and E is the

number of extinctions (including permanent emigration) on an island during the elapsed time

interval There are several ways to define I and E For example, they can be functions of island

size and the number of resident species on the island The number of parameters can quickly increase if we consider both area and number of species for each parameter Here, we consider a simple model

𝑑𝑆

rates This leads to

𝑆𝑡= 𝐼0 𝑆𝑚

𝐼0+𝐸0− �𝐼0 𝑆𝑚

number of species of the original system Substituting model (S1) into the above equation and

simplifying notation, we obtain

the main text fits our data well (R 2 = 0.783; Fig S1)

that have been used to model SAR for relatively small areas (as in our study) are the Gleason

S1), but model (S5) with the S0 Gleason SAR substitution provided a poorer fit (R2 = 0.704) We therefore only present results based on the more common power-law model in the main text

We completed all statistical analyses and figures using the R statistical package, version

2.12.2 (38)

Fig S1 Rarefied small mammal species richness in large (10.1-56.3 ha, n = 7) and small

(0.3-4.7 ha, n = 9) islands 5-7 years (dark tones) and 25-26 years (light tones) following isolation

Rarefaction was based on 10 samples for each island; islands with fewer than 10 individuals were excluded We also used rarefied levels of 5 and 8 individuals, but the results remained the same and are not reported Plotted are median values, interquartile ranges, and full ranges The upper horizontal dashed line represents the number of small mammal species found on the mainland (Table S3)

Fig S2 Mean small mammal species richness per transect in large (10.1-56.3 ha, n = 7) and

small (0.3-4.7 ha, n = 9) islands 5-7 years (dark tones) and 25-26 years (light tones) following

isolation Plotted are median values, interquartile ranges, and full ranges The upper horizontal dashed line represents the number of small mammal species found on the mainland (Table S3)

Fig S3 Predicted vs observed number of species on forest fragments Predicted number of

species is based on model (1)

y

5 1 3 1 2 1 1 6

12 1 11 1 3

X3 1 8 1

X3 1 1 10 2

Table S1 Small mammal abundance and richness per transect on islands in Chiew Larn

Reservoir Three sampling periods were made 5-7 years following isolation (1992-1994), and two were made 25-26 years following isolation (2012-2013) Total species richness per transect

is listed in the final column

Model LL k ΔAICc wAIC c %DE

Table S2 Predictors of species richness for forest fragments (years since fragment isolation and

island area) Shown are the top-ranked generalized linear models testing five potential

predictors Included for each model is maximum log-likelihood (LL), number of parameters (k),

change in Akaike’s information criterion corrected for small samples relative to the top-ranked

Table S3 Small mammal abundance and richness on mainland control sites surrounding Chiew Larn Reservoir Order, family, and

species names are listed The three same sites were surveyed 5, 6, 7, and 25 years following isolation (1992-1994, 2012); a different site was surveyed 26 years following isolation (2013) due to changes in the direction of research All sites were located adjacent to the

reservoir and within a few kilometers from other island sites Sampling methods were identical to those used on islands (18) Total

species richness per site is listed in the final column Rattus tiomanicus does not occur naturally in undisturbed forest surrounding

Chiew Larn Reservoir; all other species are native

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