![\"\"](\"https:\/\/bilimvegelecek.com.tr\/wp-content\/uploads\/2018\/10\/birinci-foto\u011fraf.jpg\")
\u201cTropikal ormanlarda do\u011fal d\u00fc\u015fmanlar\u0131n n\u00fcfusu kontrol alt\u0131nda tutulur\u201d<\/strong> Bug\u00fcne dek!<\/p>\n \u00c7al\u0131\u015fman\u0131n \u00e7\u0131kt\u0131s\u0131, t\u00fcr\u00fcn yayg\u0131n olarak bulundu\u011fu b\u00f6lgelerde pop\u00fclasyonun b\u00fcy\u00fcmesini frenleyici etki yaratan bir \u201cnegatif geribesleme\u201d oldu\u011fu y\u00f6n\u00fcnde.<\/p>\n Bulgular, 1970\u2019lerde ortaya at\u0131lm\u0131\u015f bir tahmini do\u011frular nitelikte. Bu tahmine g\u00f6re, tropikal ormanlar\u0131n \u00e7ok \u00e7e\u015fitli olmas\u0131n\u0131n nedeni, do\u011fal d\u00fc\u015fmanlar\u0131n pop\u00fclasyonlar\u0131 dengede tutuyor olmas\u0131. Brown \u00c7evre ve Toplum Enstit\u00fcs\u00fc \u00fcyesi olan Kellner, bu d\u00fc\u015fman\u0131n tohum yiyen bir hayvan, bir otobur ya da hastal\u0131k yapan bir patojen olabilece\u011fini s\u00f6yl\u00fcyor.<\/p>\n Kellner bu durumu \u015f\u00f6yle bir \u00f6rnekle a\u00e7\u0131kl\u0131yor: \u201cBir me\u015fe a\u011fac\u0131 ve bir sincap d\u00fc\u015f\u00fcn\u00fcn. Sincap, me\u015fe palamutlar\u0131n\u0131 yiyor ve yiyecek aramak i\u00e7in me\u015fe a\u011fa\u00e7lar\u0131n\u0131n \u00e7ok\u00e7a bulundu\u011fu b\u00f6lgelere y\u00f6neliyor. Bir ak\u00e7aa\u011fa\u00e7 korusu i\u00e7erisinde bulunan tek bir me\u015fe a\u011fac\u0131 sincaplar taraf\u0131ndan fark edilmiyor, dolay\u0131s\u0131yla me\u015fe korusunda \u00e7ok\u00e7a bulunan me\u015fe a\u011fa\u00e7lar\u0131n\u0131 t\u00fcketen \u201cdo\u011fal d\u00fc\u015fmanlar\u201d taraf\u0131ndan bir kontrol mekanizmas\u0131 i\u015fletiliyor. Bu t\u00fcrden bir davran\u0131\u015f, tropikal ya\u011fmur ormanlar\u0131nda yayg\u0131n oldu\u011fu takdirde t\u00fcrlerin b\u00f6lge i\u00e7erisinde yayg\u0131nla\u015fmas\u0131 engellenmi\u015f oluyor.\u201d<\/p>\n \u201cT\u00fcrlerin nadirli\u011fi\u201d<\/strong> “Tropikal ormanlarda a\u011fa\u00e7lar\u0131n \u00fcretken hale gelmesi y\u0131llar s\u00fcr\u00fcyor ve as\u0131l problem t\u00fcrlerin nadirli\u011finde birle\u015fiyor. Tek bir yeti\u015ftin a\u011faca ula\u015fabilmek ad\u0131na her y\u0131l yakla\u015f\u0131k olarak 101 hektarl\u0131k bir alanda ara\u015ft\u0131rma yapmak zorunda kald\u0131k. Bu, do\u011faya kar\u015f\u0131 bir meydan okumayd\u0131 ve y\u00fcr\u00fcyerek ba\u015far\u0131lmas\u0131 m\u00fcmk\u00fcn de\u011fildi. Bu nedenle ara\u015ft\u0131rmada havadan g\u00f6zlem y\u00f6ntemi kullan\u0131ld\u0131.”<\/p>\n Kellner ve \u00e7al\u0131\u015fman\u0131n di\u011fer y\u00fcr\u00fct\u00fcc\u00fclerinden, UCLA’da g\u00f6revli Ekoloji profes\u00f6r\u00fc Stephen Hubbell, Panama Kanal\u0131’n\u0131n ortas\u0131nda yer alan, yakla\u015f\u0131k 15.5 kilometrekarelik bir ada olan Barro Colorado’da bulunan pop\u00fclasyonu izlemek i\u00e7in 10 y\u0131ldan uzun bir s\u00fcre boyunca y\u00fcksek \u00e7\u00f6z\u00fcn\u00fcrl\u00fckl\u00fc uydu g\u00f6r\u00fcnt\u00fcleme teknolojisini kullanarak g\u00f6zlem yapt\u0131. Her y\u0131l\u0131n birka\u00e7 g\u00fcn\u00fc parlak sar\u0131 \u00e7i\u00e7ekler \u00fcreten bir tropikal ya\u011fmur orman\u0131 a\u011fac\u0131 olan Handroanthus Guayacan’\u0131 arad\u0131lar.<\/p>\n Kellner, “Bu t\u00fcr\u00fcn \u00e7i\u00e7ek a\u00e7ma mevsiminde uydu g\u00f6r\u00fcnt\u00fclerini odaklayarak t\u00fcr\u00fcn adadaki bir\u00e7ok yeti\u015fkin bireyini tan\u0131mlamay\u0131 ba\u015fard\u0131k” diyor.<\/p>\n \u201cBal\u0131k\u00e7\u0131l\u0131ktan hastal\u0131k salg\u0131nlar\u0131na ili\u015fkin tahminlerimize kadar her \u015fey i\u00e7in \u00f6nem te\u015fkil ediyor\u201d<\/strong> \u00c7al\u0131\u015fmalar\u0131n sonucunda ara\u015ft\u0131rmac\u0131lar, negatif geribeslemenin yeni yeti\u015fkin a\u011fa\u00e7lar\u0131n n\u00fcfusunun artmas\u0131n\u0131 etkiledi\u011fini ve bunun da 100 futbol sahas\u0131 b\u00fcy\u00fckl\u00fc\u011f\u00fcndeki alana yay\u0131lm\u0131\u015f olan yeni yeti\u015fkin a\u011fa\u00e7 pop\u00fclasyonunu etkileyebilece\u011fini ortaya \u00e7\u0131kard\u0131lar. Kellner bu \u00e7al\u0131\u015fman\u0131n, “b\u00f6lgede ev sahibi konumundaki floraya \u00f6zg\u00fc d\u00fc\u015fmanlar\u0131n etkilerini k\u00fc\u00e7\u00fck alanlarda s\u0131n\u0131rlayan gen\u00e7 a\u011fa\u00e7lara” ili\u015fkin \u00f6nceki \u00e7al\u0131\u015fmalar ile \u00e7eli\u015fti\u011fini de ifade etti.<\/p>\n A\u011fa\u00e7lara ait uydu verilerinin do\u011frulanmas\u0131 i\u00e7in adaya giden ara\u015ft\u0131rmac\u0131lar, ba\u011f\u0131ms\u0131z olarak da\u011f\u0131l\u0131m g\u00f6steren 123 yeti\u015fkin a\u011fac\u0131 buldular. Bu a\u011fa\u00e7lar\u0131n 89 tanesi y\u00fcksek \u00e7\u00f6z\u00fcn\u00fcrl\u00fckl\u00fc g\u00f6r\u00fcnt\u00fclerle tespit edilmi\u015fti. Bu durum, \u00e7al\u0131\u015fma i\u00e7in kullan\u0131lan verilerin ger\u00e7e\u011fe yak\u0131n sonu\u00e7lar\u0131n\u0131n oldu\u011funu g\u00f6stermektedir. Kellner, \u00e7al\u0131\u015fmaya ili\u015fkin a\u00e7\u0131klamalar\u0131n\u0131n sonunda \u015fu ifadelere yer verdi:<\/p>\n “Ekolojideki herhangi bir fikri, pop\u00fclasyon dinami\u011finden daha \u00f6nemli g\u00f6rm\u00fcyorum. Bu \u00e7al\u0131\u015fma; bal\u0131k\u00e7\u0131l\u0131ktan, hastal\u0131k salg\u0131nlar\u0131na ili\u015fkin tahminlerimize kadar her \u015fey i\u00e7in \u00f6nem te\u015fkil ediyor.”<\/p>\n
\nBrown \u00dcniversitesi’nde \u00e7al\u0131\u015fma y\u00fcr\u00fcten ve makalenin ba\u015fyazar\u0131 olan Evrimsel Biyolog Do\u00e7. Dr. Jim Kellner, “Panama\u2019da birka\u00e7 futbol sahas\u0131 b\u00fcy\u00fckl\u00fc\u011f\u00fcndeki bir alanda, Kuzey Amerika ve Meksika\u2019n\u0131n kuzeyindekinde oldu\u011fundan \u00e7ok daha fazla say\u0131da a\u011fa\u00e7 t\u00fcr\u00fc var” diyor ve a\u00e7\u0131klamalar\u0131n\u0131 \u015f\u00f6yle s\u00fcrd\u00fcr\u00fcyor: “Bu \u00e7e\u015fitlili\u011fin nas\u0131l ortaya \u00e7\u0131kt\u0131\u011f\u0131 ve zaman i\u00e7erisinde neden s\u00fcregeldi\u011fi sorusu y\u00fczy\u0131l\u0131 a\u015fk\u0131n bir s\u00fcredir do\u011fa bilimcilerinin g\u00fcndemini me\u015fgul eden bir paradokstu.”<\/p>\n
\n“Konuya ili\u015fkin ilk \u00e7al\u0131\u015fmalar bahsi ge\u00e7en negatif geribeslemenin, gen\u00e7 a\u011fa\u00e7lar\u0131 -tohumlar, fideler ve fidanlar\u0131- etkiledi\u011fi y\u00f6n\u00fcndeydi. Ancak ekolojistler; yeti\u015fkin a\u011fa\u00e7lar\u0131n, pop\u00fclasyonlar\u0131n \u00fcretken bireylerinin de bu negatif geribesleme etkilenip etkilenmedi\u011fini belirleyememi\u015flerdi.<\/p>\n![\"\"](\"https:\/\/bilimvegelecek.com.tr\/wp-content\/uploads\/2018\/10\/ikinci-foto\u011fraf.jpg\")
\nAra\u015ft\u0131rmac\u0131lar, bu tekni\u011fi kullanarak bahsi ge\u00e7en t\u00fcre ait 1.006 yeti\u015fkin a\u011fac\u0131n varl\u0131\u011f\u0131n\u0131 ortaya \u00e7\u0131kard\u0131lar. 10 y\u0131ll\u0131k \u00e7al\u0131\u015fma periyodunda, Kellner ve Hubbell, yeni a\u011fa\u00e7lar\u0131n yeti\u015fkin a\u011fa\u00e7 pop\u00fclasyonuna ilk kez kat\u0131ld\u0131klar\u0131 evreyi belirlediler. Ara\u015ft\u0131rmalar\u0131nda arada bir y\u0131l\u0131 \u00e7i\u00e7eklenmeden ge\u00e7iren veya erken ya da ge\u00e7 \u00e7i\u00e7eklenen bitkileri de\u011fil de “yeni yeti\u015fkinleri” belirlediklerinden emin olmak i\u00e7in ileri istatistiksel y\u00f6ntemler kulland\u0131lar.<\/p>\n