The Role of Small Lowland Patches of Exotic Forests as Refuges of Rare Endemic Azorean Arthropods

Round 1

Reviewer 1 Report

The paper addresses some fundamental problems of biodiversity protectyion and management in an island, the habitat value of exotic lowland forests, and the hypotheses put forward are clear and well answered. The method (SLAM traps) used for the arthropod monitoring is perhaps strongly oriented to good fliers or species with high dispersal power, a fact that is surely in part responsible for the surprising diversity of endemic and native species in exotic forest remnants, in the conclusions this fact should be emphasized and enclosed in the needs for future research, because on the islands a high percentage of endemics is found in the soil living fauna, like ground beetles, weevils, and several other coleopteran families, especially on mountain slopes and tops, see f.e. the paper of Borges et al, 2017, Biodiversity Data Journal 5: e14557.

at line 258: Aloconota sulcifrons

The paper should be accepted in the present form, possibly with my suggestion about the limits of the methos used.

Author Response

The paper addresses some fundamental problems of biodiversity protectyion and management in an island, the habitat value of exotic lowland forests, and the hypotheses put forward are clear and well answered.

Authors: Thank you for your encouragement.

 

The method (SLAM traps) used for the arthropod monitoring is perhaps strongly oriented to good fliers or species with high dispersal power, a fact that is surely in part responsible for the surprising diversity of endemic and native species in exotic forest remnants, in the conclusions this fact should be emphasized and enclosed in the needs for future research, because on the islands a high percentage of endemics is found in the soil living fauna, like ground beetles, weevils, and several other coleopteran families, especially on mountain slopes and tops, see f.e. the paper of Borges et al, 2017, Biodiversity Data Journal 5: e14557.

Authors: Thank you for this comment. We agree that SLAM traps are oriented to species with high dispersal ability but we found also some species highlighted in discussion with poor dispersal ability. Indeed, the SLAM traps were fixed in the soil and they also captured arthropods moving on the ground. The poor dispersive species captured have relict populations restricted to low elevation. However, we stressed this in the conclusions for further studies to add also sampling methods oriented for species with lower dispersal capabilities.

Text added in line 461-463: “Although, some species with lower dispersal ability were trapped in this study, SLAM traps are mostly oriented toward higher dispersive species. Thus, additional sampling protocols should be implemented in lowland exotic forests to uncover the spatial distribution of additional rare and specialized species among soil adapted arthropods.”

 

at line 258: Aloconota sulcifrons

Authors: Thank you, we corrected the species name

 

The paper should be accepted in the present form, possibly with my suggestion about the limits of the methos used.

Authors: Thank you for your positive comment.

Reviewer 2 Report

Dear Authors,

thank you for your interesting contribution, it was a pleasure to revise your draft.

I have only two major questions that I would like to get addressed:

1)Sampling Spiders with SLAM traps does not sound exactly as the best method to investigate spider diversity, especially on islands. I retain that your data collection may potentially have resented of a sampling bias, since I would not really expect native and especially endemic spiders to disperse via ballooning or by wind in general (because counterselected on islands); consequently your traps may overestimate the abundance of  "flying" generalist spiders agains native randomly collected.

Please correct me if I got it wrong.

2) Did you explore the altitude effect on traps catch abundance and composition? I did not find any ref. into the text. Checking on the map provided in the S1 it appears you are grouping and comparing similar forest patches but sampled at different altitudes; don't you think that the different chances in the microhabitats may effect species diversity and abundance also?

Sincerely

Comments for author File: Comments.pdf

Author Response

Dear Authors,

thank you for your interesting contribution, it was a pleasure to revise your draft.

Authors: Thank you

I have only two major questions that I would like to get addressed:

1) Sampling Spiders with SLAM traps does not sound exactly as the best method to investigate spider diversity, especially on islands. I retain that your data collection may potentially have resented of a sampling bias, since I would not really expect native and especially endemic spiders to disperse via ballooning or by wind in general (because counter selected on islands); consequently your traps may overestimate the abundance of  "flying" generalist spiders against native randomly collected.

Please correct me if I got it wrong.

Authors: Thank you for raising this point which also meet the comments of reviewer 1. We agree that SLAM traps are oriented to species with high dispersal ability but we found also some species highlighted in discussion with poor dispersal ability. Indeed, the SLAM traps were fixed in the soil and they also captured arthropods moving in the soil. The poor dispersive species captured have relict populations restricted to low elevation. However, we stressed this in the conclusions for further studies to add also sampling methods for species with lower dispersal capabilities.

Text added in line 464: “Although some species with lower dispersal ability were trapped in this study, SLAM traps are mostly oriented toward higher dispersive species. Thus, additional sampling protocols should be implemented in lowland exotic forests to uncover the spatial distribution of further rare and specialized species among soil adapted arthropods.”

 

2) Did you explore the altitude effect on traps catch abundance and composition? I did not find any ref. into the text. Checking on the map provided in the S1 it appears you are grouping and comparing similar forest patches but sampled at different altitudes; don't you think that the different chances in the microhabitats may effect species diversity and abundance also?

Authors: Thank you for this comment. In our study area, exotic forest fragments are mostly located in low lands compared to native forests that are at high elevation. Therefore, it is not possible to test elevational gradient with this study design. However, in a different study submitted lately to another Journal, we tested the effect of elevation within native forests sites.

Sincerely

ATTCHED FILE WITH COMMENTS AND CORRECTIONS

Authors: Thank you very much for your corrections, we have introduced them in the text.

Line 33: please organize them in alphabetic order

Authors: Done.

Line 46: Colonized by the European since the Fifteenth century, the Azorean islands (Portugal) are exemplary of the impact of alien insects on island faunas

Authors: We rephrased the sentence as “Colonized by the European since the Fifteenth century, the Azorean is lands (Portugal) is an example of the impact of alien insects on island faunas.”

 

Line 50: Recent evidence shows that instead of a direct general insect decline, with the Azorean islands are experiencing the decline of few native species and a general increase of exotic arthropod species diversity in pristine native habitats [20].

Authors: Thank you, we deleted this part.

 

Line 56: Furthermore, due to their past adaptation to island native habitats, endemic arthropod species might capture biodiversity trends on islands better than exotic species.

Authors: Thank you, we deleted this part.

 

Line 58: In the Azores islands, natural protected areas are essentially forest ecosystems.

Authors: Thank you, we deleted this part.

 

Line 60: please add family and describer name

Authors: We added this information in Table S1 and specified it in materials. Now it reads as

“Fifteen sites were located in native forest areas encompassing the five extant forest fragments and 21 sites included all exotic trees sites (Figure S1, taxonomic details are given in Table S1)”.

 

Line 64: pasture lands

Authors: Thank you, we corrected.

 

Line 66: I would say “patches of native vegetation” — in my opinion only “native vegetation” seems to refer only to phytophylous species

Authors: We agree and added this description.

 

Line 84: “in the respect of”

Authors: Added.

 

Line 112: add describer and family

Authors: We added the authorities and families in 2.1 section. We also added this information in Table S1 and specified it in materials.

 

Line 114:

“on”;

…from wind but this species became one of the worst invasive species in the Azores after the abandonment of orange production.

Authors: corrected. Thank you.

 

Line 123:

These arthropod groups play key roles in the ecological processes of forest ecosystems 123 and their diversity, taxonomy and ecology is well known in the Azores. ;

May be “for”

Authors: corrected. Thank you.

 

Line 128: what hight?  are data comparable?

what is the area of forest covered by a sigle trap?

Authors: Thank you for these questions. Now we say in the manuscript that the traps were fixed to the ground and covered an area of at least 5 m x 5 m. The sentence now reads as follows:

 

“We sampled the target groups by using SLAM (Sea, Land, and Air Malaise) traps fixed to the soil and covering an area of at least 5m x 5m or larger depending on the density of trees in the forest.  SLAM is a type of passive flight interception trap suitable to sample mobile arthropods.”

 

Line 173: This is not fully clear to me; you previously said that the fauna is well known, than what is the point to stick to morphospecies? you’re missing information there. Than subsequently you talk about species…

Authors: We found in our sampling a few species that were not identified yet. Since we added those taxa in our study, we decided to use the nomenclature (morpho)species to indicate that some taxa have not yet a binomial identifier. We now added a sentence in the Methods to clarify this:

“When identification was not possible we kept a morphospecies identifier to a given taxon”.

 

Line 193: better “exotic” than “introduced”

Authors: All over the text, we used the term “introduced” to refer to exotic species. We think it is better to keep “introduced” for the coherence of the text.

 

Line 236: add describer and family, or mention in matherials and methods that describers and families are given in S1

Authors: We added this information in Table S1 and specified it in materials and method section line 115.

 

Line 245: are you sure they all belong to the same species? if sure, state it and do not mention morphospecies, if not exclude it form the analyses

Authors: Many thanks for mentioning this. Indeed there was a mistake here and we completely revised the test accordingly with the results in Tables S2, S3 and S4.

 

Line 256: Out of the thirty native non-endemic beetle species sampled in this study, sixteen were present only in exotic forest and three where present only in the native forests

Authors: corrected. Thank you.

 

Line 289, 306, 321, 369: I know that this bold word is wanted, but I am not sure if agrees with MDPI guidelines

Authors: Removed for now

 

Line 390: However, we also found that some lowland patches of exotic forests can sustain rare endemic species.

Authors: corrected. Thank you.

 

Line 403, 413. 428: (see also [37].) ; (see also [26,31]); (see [9].)

Authors: We replaced with respectively: See also Borges et al, 2017 [37]; see also Cardoso et al, 2009 [26] and Meijer et al, 2011 [31]; see Terzopoulou et al, 2015 [9]

Line 414: I would say “ideally”

Authors: Thank you. We added the word “ideally”.

Line 538: this is latin, thus use italics

Authors: Thank you. Corrected.

Line 539: “our”

Authors: Thank you. We corrected.

Reviewer 3 Report

The authors compared species composition of several insect groups distributed in native and exotic forest growths in Azores. The authors found very interesting results - also exotic forests host important spectre of native species, including endemics. Even more, the diversity of endemic Psocoptera is higher in exotic than native forests.

The paper is well organised, well written and the analyses are easy to follow.

There is only one thing, which I lack in the paper - a mechanism, how it can happen. The explanations may be relatively easy. Many of the species may be not directly tight to tree species, but rather to forest conditions  (herb composition, shade, higher humidity etc.) irrespective of tree species composition. Also some endemic species in Azores do not occur in forests at all as they inhabit open habitats, rock cliffs etc., but a reader of the paper may got feeling that only forests cover matters. Thus, I would welcome a short additional comment on it. Otherwise the paper is very nice and really worth of publishing.

Author Response

The authors compared species composition of several insect groups distributed in native and exotic forest growths in Azores. The authors found very interesting results - also exotic forests host important spectre of native species, including endemics. Even more, the diversity of endemic Psocoptera is higher in exotic than native forests.

The paper is well organised, well written and the analyses are easy to follow.

Authors: Thank you for your positive comments

 

There is only one thing, which I lack in the paper - a mechanism, how it can happen. The explanations may be relatively easy. Many of the species may be not directly tight to tree species, but rather to forest conditions  (herb composition, shade, higher humidity etc.) irrespective of tree species composition.

Authors: Thank you. We added this explanation in the text. In line 446:

“There is no clear explanation of the importance of these sites. One hypothesis might be the proximity with a native forest fragment for one site and the fact that the two other sites replaced ancient native forest fragments, or, more broadly, the environmental conditions (herb composition, shade, higher humidity, etc.) provided in the forest site.”

 

Also some endemic species in Azores do not occur in forests at all as they inhabit open habitats, rock cliffs etc., but a reader of the paper may got feeling that only forests cover matters. Thus, I would welcome a short additional comment on it.

Authors: Thank you for your comment. We agree even if most of species are found in forest habitat some might be supported by open habitats, rock cliffs. We stressed that point in the conclusions: Lines 458-460: Knowing that some endemic species in the Azores do not occur in forests habitats but in open habitats, rock cliffs etc, we suggest future studies to fully understand endemic species distribution.

Otherwise the paper is very nice and really worth of publishing.

Authors: Thank you.

 

We are grateful to the three Reviewers for their useful comments. We have acknowledged the Reviewers in the Acknowledgments section.

We hope that you are satisfied with this revision and that the ms is now in a suitable form for publication.

All the best,

Paulo Borges

(on behalf of all coauthors)